iPhone isn't ringing for incoming calls, just shows missed calls

Check where the call audio is going as well. If an Apple Watch, AirPods or the car is connected over Bluetooth, the call can be getting sent there and the phone itself stays quiet. Turn Bluetooth off for a minute and get someone to ring you. And it sounds obvious, but check Settings > Sounds & Haptics, the ringer volume slider can be right down even with the switch on ring.

Go through these in order, it's nearly always one of them: - a Focus is on (moon or other icon in Control Centre). Sleep schedules turn one on automatically - Settings > Apps > Phone > Silence Unknown Callers. That sends everyone not in your contacts straight to missed - the side switch or Action button is set to silent - call forwarding switched on by the carrier If only some callers ring, it's the unknown callers setting.