iPhone 12 not ringing

1. Check to see that the Silent switch is not set to ON. Silent switch is located on the Top Left Side of your iPhone.
2. Open Settings ➔ Sounds & Haptics ➔ Ringer and Alerts : Make sure this is not set to OFF or too Low. Set Change with Buttons to OFF. Below that Make sure that there is a Ringtone selected.
3. Check to see that Do Not Disturb is set to OFF. Open Settings ➔ Do Not Disturb : Set this to OFF
4. Check to see that Silence Unknown Callers is set to OFF. Open Settings ➔ Phone ➔ Silence Unknown Callers : Set this to OFF
5. Make sure that a ringer sound is assigned. Open Settings ➔ Sounds & Haptics ➔ Ringtone : Ensure that a Ringtone is assigned here.
6. If all of the above is OK on your iPhone then Try and Force Restart your iPhone EXACTLY as shown below and see whether that resolves the issue:

• Press and quickly release Volume UP button
• Press and quickly release Volume DOWN button
• Press and Hold the SIDE button until an Apple logo appears and then release the Side button (Can take up to 20 seconds. (DO NOT release Side Button when invited to Slide Power OFF). 

Axel F.

On the left side of the phone is a small ringer button, just above the two volume buttons.

If you have a case that covers that ringer button it may not be toggled to the correct Mode.

You have the option to have Silent Mode on or Silent Mode off.

Slide it to Silent Mode OFF.

Then follow the instructions that you see that others have provided below.

That seems to be the reason a lot of people are having trouble, they do not see the ringer button, and they have the wrong type of cover which covers that switch. Hope this helps.