Today I tried to ried to reproduce the issue by Creating a brand new sandbox Apple ID with region pointing to USA Set device region to USA Restart device Adding the first Amex test card in apple list 3717 377570 42005, Expiration Date: Any, CID: 1111 And it resulted in a success. Possible reason why it didn’t work at the beginning may be attributed to Amex/card scheme servers irregular outages.

I forgot to add a screenshot but this is the error

We are having the same issue For American Express cards, as of June 2024, no test cards can be added to the Sandbox Apple wallet and got this error. has reached out to Apple Pay Support. The device region, test account, app store settings are all pointing to United States as region