Why can't I send short messages after my Shenzhouxing card is converted to GSM? I can accept text messages, talk normally, and I haven't answered the phone for the time being.

In this case, the short message function is generally limited. Have you sent text messages in groups recently? Generally, there are many such situations. If so, you can ask and tell you the details. If not, there is another possibility that your SMS center number is wrong. The number of the National SMS Center is 13800XYZ500, where XYZ is your local area code. For example, Beijing area code 0 10 uses 100, Nanjing 025 uses 250 (add 0 to the last two digits), and Wuxi 05 10 uses 5 10 (remove the last three digits). Please set it up and try it.