Can't Add American Express Cards to Apple Wallet
I have 4 cards, American Express charge and credit cards, and Visa credit and debit cards, registered with my Apple ID. Up till yesterday all 4 cards were available in Wallet on both my iPhone and Apple Watch.
The latest WatchOS update said I needed to unpair and repair my watch and phone, which I did. After re-pairing, I was able to re-add my two Visa cards to the watch's wallet, but both American Express cards give an error after entering the (correct) security code: "Could Not Add Card; Try again later or contact the issuer for more information".
In searching for a solution I found a post that said disabling the phone's passcode then re-enabling it fixed the issue for people who couldn't add cards to the phone's wallet. I wondered if it might fix the watch problem, too, so I tried it. As I have Touch ID enabled, I didn't expect disabling the passcode to remove all the cards from the phone's wallet, but it did. After re-enabling it, I was able to re-add both Visa cards to the phone's wallet, but—you guessed it—I now get the same error when trying to add my American Express cards to the phone's wallet, too. All this was working a day ago.
The American Express iOS app allows you to add cards to the device's wallet from within the app, and this also fails with the same error. I'm stuck.
Thanks in advance for any suggestions.
iPhone SE