It works for me now and my account has been replenished with coins owed to me. I’m not sure if it will work for everyone.
I enabled Apple Cash. Put 30 dollars into it via my bank account. And made Apple Cash my default payment instead of the credit card that I had been using.
I signed into Pokémon Go using the account that I have always had (Google account) went into the settings and linked my Apple Account option.
I signed out of Pokémon Go, closed the app and restarted my iPhone.
I then signed back into Pokémon Go through my original Google account. Checked the shop and my 108 dollars (14,500) coins that I paid for over a week ago, had been replenished into my Pokémon Go coin bank.
I checked my Apple Cash account on my iPhone and the balance was still 30 dollars. That being said, I went into the Pokémon Go shop, scrolled all the way down to the coins and bought the $4.99 option.
It went through and was debited from default Payment Apple Cash account and coins were added.
note: not sure if this is important or not, but I disabled the feature where it needs facial recognition to authenticate you buying coins. I did it to where I have to enter my Apple ID password manually.
Anyways, it works for me. Hopefully you all have joy once again in your lives!