You may get a high failure rate while sending messages if you are trying to send them too fast. You can try to configure the app as shown here to decrease the number of failed messages.
If you are sending MMS messages, then make sure SMS Gateway is set as default app for sending SMS. If it isn't, then you can set it as default by following the below guide.
Some countries have different rules for mobile number formatting while sending messages. The badly formatted mobile number is also one of the reasons for failed response. You can check out the guide from here to see how to format mobile numbers while sending messages.
Sometimes operators can ban your SIM for sending too many messages, or they can have a rate limit on the number of messages you can send in a certain time frame. In this case, using higher delay between messages can prevent failures.
Every network operator works differently, and a "Failed" response is given by the network operator. It usually happens when your network operator can't reach the mobile number. You can try changing the sim card or using the same sim on another device.
There is nothing you can do about it if you are still getting a failed response from the network operator after trying all the instructions provided above. You can check out the error code list shown below to get the reason for failure.
| NO_SERVICE | Your device simply has no cell reception. You're probably in the middle of nowhere, somewhere inside, underground, or up in space. Certainly away from any cell phone tower. Sometimes it also happens when you get a call while sending messages. |
| RADIO_OFF | You switched your device into airplane mode, which tells your device exactly "turn all radios off" (cell, wifi, Bluetooth, NFC, ...). |
| LIMIT_EXCEEDED | Failed because the phone reached the sending queue limit. |
| GENERIC_FAILURE | Something went wrong and there's no way to tell what, why or how. |
| GENERIC_FAILURE [1] | This cause indicates that the destination requested by the Mobile Station cannot be reached because, although the number is in a valid format, it is not currently assigned (allocated). |
| GENERIC_FAILURE [8] | This cause indicates that the MS has tried to send a mobile originating short message when the MS’s network operator or service provider has forbidden such transactions. |
| GENERIC_FAILURE [10] | This cause indicates that the outgoing call barred service applies to the short message service for the called destination. |
| GENERIC_FAILURE [17] | This cause is sent to the MS if the MSC cannot service an MS generated request because of PLMN failures, e.g. problems in MAP. |
| GENERIC_FAILURE [21] | This cause indicates that the equipment sending this cause does not wish to accept this short message, although it could have accepted the short message since the equipment sending this cause is neither busy nor incompatible. |
| GENERIC_FAILURE [27] | This cause indicates that the destination indicated by the Mobile Station cannot be reached because the interface to the destination is not functioning correctly. The term “not functioning correctly” indicates that a signaling message was unable to be delivered to the remote user; e.g., a physical layer or data link layer failure at the remote user, user equipment off-line, etc. |
| GENERIC_FAILURE [28] | This cause indicates that the subscriber is not registered in the PLMN (i.e. IMSI not known). |
| GENERIC_FAILURE [29] | This cause indicates that the facility requested by the Mobile Station is not supported by the PLMN. |
| GENERIC_FAILURE [29] | This cause indicates that the facility requested by the Mobile Station is not supported by the PLMN. |
| GENERIC_FAILURE [30] | This cause indicates that the subscriber is not registered in the HLR (i.e. IMSI or directory number is not allocated to a subscriber). |
| GENERIC_FAILURE [38] | This cause indicates that the network is not functioning correctly and that the condition is likely to last a relatively long period of time; e.g., immediately reattempting the short message transfer is not likely to be successful. |
| GENERIC_FAILURE [41] | This cause indicates that the network is not functioning correctly and that the condition is not likely to last a long period of time; e.g., the Mobile Station may wish to try another short message transfer attempt almost immediately. |
| GENERIC_FAILURE [42] | This cause indicates that the short message service cannot be serviced because of high traffic. |
| GENERIC_FAILURE [47] | Resources unavailable. This cause is used to report a resource unavailable event only when no other cause applies. |
| GENERIC_FAILURE [50] | This cause indicates that the requested short message service could not be provided by the network because the user has not completed the necessary administrative arrangements with its supporting networks. |
| GENERIC_FAILURE [69] | This cause indicates that the network is unable to provide the requested short message service. |
| GENERIC_FAILURE [81] | This cause indicates that the equipment sending this cause has received a message with a short message reference which is not currently in use on the MS-network interface. |
| GENERIC_FAILURE [95] | This cause is used to report an invalid message event only when no other cause in the invalid message class applies. |
| GENERIC_FAILURE [96] | This cause indicates that the equipment sending this cause has received a message where a mandatory information element is missing and/or has a content error (the two cases are indistinguishable). |
| GENERIC_FAILURE [97] | This cause indicates that the equipment sending this cause has received a message with a message type it does not recognize either because this is a message not defined or defined but not implemented by the equipment sending this cause. |
| GENERIC_FAILURE [98] | Message not compatible with short message protocol state |
| GENERIC_FAILURE [99] | This cause indicates that the equipment sending this cause has received a message which includes information elements not recognized because the information element identifier is not defined or it is defined but not implemented by the equipment sending the cause. However, the information element is not required to be present in the message in order for the equipment to send the cause to process the message. |
| GENERIC_FAILURE [111] | This cause is used to report a protocol error event only when no other cause applies. |
| GENERIC_FAILURE [127] | This cause indicates that there has been interworking with a network that does not provide causes for actions it takes; thus, the precise cause for a message which is being sent cannot be ascertained. |
| GENERIC_FAILURE [128] | Telematic internetworking not supported |
| GENERIC_FAILURE [129] | Short message type 0 not supported |
| GENERIC_FAILURE [130] | Cannot replace short message |
| GENERIC_FAILURE [143] | Unspecified TP-PID error |
| GENERIC_FAILURE [144] | Data code scheme not supported |
| GENERIC_FAILURE [145] | Message class not supported |
| GENERIC_FAILURE [159] | Unspecified TP-DCS error |
| GENERIC_FAILURE [160] | Command cannot be actioned |
| GENERIC_FAILURE [161] | Command unsupported |
| GENERIC_FAILURE [175] | Unspecified TP-Command error |
| GENERIC_FAILURE [176] | TPDU not supported |
| GENERIC_FAILURE [192] | SC busy |
| GENERIC_FAILURE [193] | No SC subscription |
| GENERIC_FAILURE [194] | SC System failure |
| GENERIC_FAILURE [195] | Invalid SME address |
| GENERIC_FAILURE [196] | Destination SME barred |
| GENERIC_FAILURE [197] | SM Rejected-Duplicate SM |
| GENERIC_FAILURE [198] | TP-VPF not supported |
| GENERIC_FAILURE [199] | TP-VP not supported |
| GENERIC_FAILURE [208] | D0 SIM SMS Storage full |
| GENERIC_FAILURE [209] | No SMS Storage capability in SIM |
| GENERIC_FAILURE [210] | Error in MS |
| GENERIC_FAILURE [211] | Memory capacity exceeded |
| GENERIC_FAILURE [212] | Sim application toolkit busy |
| GENERIC_FAILURE [213] | SIM data download error |
| GENERIC_FAILURE [255] | Unspecified error cause |
| GENERIC_FAILURE [300] | ME Failure |
| GENERIC_FAILURE [301] | SMS service of ME reserved |
| GENERIC_FAILURE [302] | Operation not allowed |
| GENERIC_FAILURE [303] | Operation not supported |
| GENERIC_FAILURE [304] | Invalid PDU mode parameter |
| GENERIC_FAILURE [305] | Invalid Text mode parameter |
| GENERIC_FAILURE [310] | SIM not inserted |
| GENERIC_FAILURE [311] | SIM PIN required |
| GENERIC_FAILURE [312] | PH-SIM PIN required |
| GENERIC_FAILURE [313] | SIM failure |
| GENERIC_FAILURE [314] | SIM busy |
| GENERIC_FAILURE [315] | SIM wrong |
| GENERIC_FAILURE [316] | SIM PUK required |
| GENERIC_FAILURE [317] | SIM PIN2 required |
| GENERIC_FAILURE [318] | SIM PUK2 required |
| GENERIC_FAILURE [320] | Memory failure |
| GENERIC_FAILURE [321] | Invalid memory index |
| GENERIC_FAILURE [322] | Memory full |
| GENERIC_FAILURE [330] | SMSC address unknown |
| GENERIC_FAILURE [331] | No network service |
| GENERIC_FAILURE [332] | Network timeout |
| GENERIC_FAILURE [340] | No +CNMA expected |
| GENERIC_FAILURE [500] | Unknown error |
| GENERIC_FAILURE [512] | User abort |
| GENERIC_FAILURE [513] | Unable to store |
| GENERIC_FAILURE [514] | Invalid Status |
| GENERIC_FAILURE [515] | Device busy or Invalid Character in string |
| GENERIC_FAILURE [516] | Invalid length |
| GENERIC_FAILURE [517] | Invalid character in PDU |
| GENERIC_FAILURE [518] | Invalid parameter |
| GENERIC_FAILURE [519] | Invalid length or character |
| GENERIC_FAILURE [520] | Invalid character in text |
| GENERIC_FAILURE [521] | Timer expired |
| GENERIC_FAILURE [522] | Operation temporary not allowed |
| GENERIC_FAILURE [532] | SIM not ready |
| GENERIC_FAILURE [534] | Cell Broadcast error unknown |
| GENERIC_FAILURE [535] | Protocol stack busy |
| GENERIC_FAILURE [538] | Invalid parameter |
| UNKNOWN_ERROR [*] | Something went wrong and there's no way to tell what, why, or how. |