How to resolve new user access issue

Added new user to my AWS account. User received email with login instructions. When clicked on link, the user was directed to the "New User Sig Up" screen with request to enter a new password. But the user keeps getting error message "It's not you, it's us. We couldn't complete your request right now. Please try again later". The user has attempted to login multiple times at different times. I've deleted the user and added twice. Keeps getting the same error message. Please help!