My iPhone 12 will not charge wirelessly why?

If you're using a Qi certified or a MagSafe charger AND if your already tried all the steps provided in the support article than led you here, I suggest that you make an appointment (*) and have your device + charger inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector. After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.