How to fix the grayed out wifi button and bluetooth button that is loading?

(1) 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). 

(2)  If that does not help then take advantage of the Apple 1YR Warranty that should still be in effect on your iPhone 12 and have it examined at the Apple Store or at an Authorized Service Center for further resolution. You may also ➔  Contact Apple for support and service - Apple Support

Axel F.

It will be part of the warranty if there is no user caused damage to the iPhone. Best bet is to stay your course and visit the Apple Store. They will guide you in the right direction.

Note - I do not work for Apple and neither do the users who write and respond to the posts in this community.

Axel F.

They will fix it since the iPhone is still under warranty.

Axel F.

You are welcome.

Axel F.