MagSafe charger not charging my iPhone 12 pro

Make sure that the power outlet is working. Make sure that the part that plugs into the power outlet is working.

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). 

Try charging with the MagSafe charger after the above action has been taken successfully.

Axel F.

Restart your iPhone then try again.

Force restart iPhone - Apple Support