My s21 plus does not charge thru port and Sim card is not detected. I replaced the charge port board and still the same. Wifi works but no phone connection.
visit authorized repair center for hardware check up please. SIM reading and charging issue could be hardware related.
Some other things you can try are:
1. reproduce the issue then submit error report to samsung using Samsugn Members app > get help > error report
2. Factory Reset the device and see if it helps