Iphone 12 phone ringer- it’s off. How to turn it on?

Check the Mute switch on the left side of the phone, near the top. It should be towards the screen.

Check the volume settings, using the 2 buttons below the Mute switch.

Check the Do Not Disturb setting in the Control Center (open it by dragging down from the battery icon). The button in the green circle controls Do Not Disturb:

Some things to check:

The ring/silent switch on the left side of the phone. See the following Apple article: Select ringtones and vibrations on iPhone - Apple Support

Check the ringer volume at Settings > Sounds & Haptics > Ringtone & Alert Volume.

Settings > Phone > Silence Unknown Callers. See: Detect and block spam phone calls - Apple Support

Do Not Disturb. See: Use Do Not Disturb with Focus on your iPhone or iPad - Apple Support

If none of the above, also try restarting. See instructions in: Restart your iPhone - Apple Support

See this from the iPhone User Guide.

Adjust the volume on iPhone - Apple Support

Hello ~ Any help here by clicking on below?

If you can't hear any sound or hear distorted sound from your iPhone, iPad or iPod touch speaker - Apple Support

~Katana-San~