I’ve had nothing but problems with wireless charging with the iPhone 12 Pro. The Samsung fast charger I’ve used with the Galaxy S8+, iPhone X, XS Max and 11 Pro without issues would not work with the 12 Pro. I tried it with multiple cases and without cases, purchased 4 different Qi wireless chargers, nothing worked. I had my device exchanged twice. This current device seems to work ok, but it’s much more temperamental than the other phones.
Side note: I’m using a UAG Monarch case with the 12 Pro, the same case I’ve used with all of the other phones listed above. I’ve never had an issue using this case with ANY Qi wireless charger. With the 12 Pro UAG Monarch case, the only wireless charger that will work is the Anker fast charging pad. Nothing from Samsung, Mophie, Belkin or Tylt works. The case looks the same as previous designs (different than the 11 Pro’s, though). I really think it has something to do with the internal design/magnets of the iPhone 12 models.