Why can't I send an appointment message and a regular message?

This is sometimes related to the signal quality of his mobile phone. You set up a message report, and he can't reply until he receives it, so he will reply for a long time when the signal is poor. If you can send it before, but you can't now, all you can do is check the settings of your mobile phone and whether the SM card is damaged. Finally, the signal transmission problem of network operators. The problem of network operators is generally that the capacity of your base station is insufficient, resulting in crowded user channels in the base station area.