Russia, Fenix 6X sapphire. I have same problem with a blank screen. When I "get startted" and don't add card. I cleaned cache and logoff GMC, when I logon - I view separatly menu item Garmin Pay!
It also did not work for me when my phone language was set to native language. When i switched my phone language to English, changes also app language and after that it worked with first try, i was able to add a card without errors.
