Android Pay is perhaps the most exciting aspect of Android Wear 2.0, but it has some caveats. It won't work if your phone has an unlocked bootloader, much to the disappointment of custom ROM and root users. Now it appears that some cards already compatible with Android Pay won't work on watches - namely CITI and Wells Fargo cards.

There isn't a specific subset of CITI and Wells Fargo cards that won't work - all of them are currently not supported. Here's a full list:

CITI Cards:
  • Citi Visa Credit
  • Citi MasterCard Debit and Credit
  • Co-branded: Hilton Visa Credit
  • Expedia MasterCard and Visa Credit
  • Costco AnyWhere Consumer
  • AT&T Mastercard

Wells Fargo Cards:

  • Consumer Debit Visa
  • Consumer Credit Visa and American Express
  • Small Business Credit and Debit Visa

The page only says, "at this time, these cards aren't supported on Android Wear," not providing any timeline for when they will work. It's not clear either why only these two services aren't compatible - perhaps there is some re-certification process for Android Wear. Regardless, all other Android Pay banks and cards are advertised as fully compatible with Wear.

Google's support page has been updated to reflect that, of the nine card types that worked with Android Pay but not Android Wear, now only Citi debit cards remain incompatible with AW2.0.