If you encounter the following error message, there are several possible reasons for this.
Error 51
If the issue only happens to one particular number, it could be due to a number of reasons - the number may be out of service, disconnected, or the carrier may be reporting an error making the call or text. Alternatively, it is also possible that your contact has blocked you or there are some other restrictions that we cannot check at this point of time.
We advise to double check if the number is correctly entered on your app, and that the number is in service and is has SMS capabilities. See: