Combine IAM user with existing QuickSight user

Hello, My organization has a QuickSight account where most of our users are just on QuickSight but a few are connected through their IAM user. We have one user with an existing account on QuickSight, whose email was recently registered to an IAM user and it is now preventing that user from accessing their QuickSight account. Error when logging into QuickSight: "The username already exists in this account."

I think this can be solved by removing the IAM user and recreating it with a different email but I think an Ideal solution would be to have the option to merge an existing QuickSight user with an IAM user. Does anyone know if something like that is possible?

Thanks!