First, make sure that the charger and charging cable are working properly, you can try to use other devices to charge to rule out this possibility.
Second, check whether the charging port of the Apple 13 is clean and there is no dust or foreign matter blocked. If so, you can wipe it down with a clean soft cloth. Alternatively, try restarting the phone or updating the system to fix possible software issues. If the above methods have no effect, it is recommended to contact Apple's official customer service or to a professional maintenance point for maintenance as soon as possible.