What I'm seeing in a lot of the posts is incompatibility with some wireless chargers. They may not output enough power. They may have their charging coils in the wrong location, since iPhone 12 phones now have the coil for charging directly in the center of the phone for use with a Magsafe charger if someone wants to invest in that.
I would imagine the charger you own is either a single coil Qi charger or the coils are too low to effective connect with the center coil in the back of the phone. I had one charger which was single coil. It didn't charge our iPhone 12 or iPhone 12 Pro. Our other chargers output a higher wattage and are dual coil, so they seem to work.
You may need to buy a better quality charger, with higher output and dual coils.