I would first try it in another phone, see if it picks it up. I've had this issue previously in two Huawei phones though. Both phones stopped recognizing my sim card. Switched to samsung now and haven't had an issue in a few years.
If it doesn't pick up your sim in other phones though you likely just need a new SIM card. Make sure it's not dirty and seated correctly in the phone as well. A good drop has slightly lodged it out of place for me before.
