Customers not able to login to the community

I let customers pay through Surecart and than give them access to the community. Customers report back that they are not able to login with the created credentials they used in Surecart checkout into the community. They need to reset password after sign up.

Also sometimes I saw when trying to login in to the community sometimes it gives an un ending redirect loop in the fluent community default login page. No error message that password was incorrect it just keeps redirecting to the login page. This happenend also sometimes by switching accounts. It was solved sometimes by going into private mode.

I am receiving constantly emails that user are password reseting. Anyone know what the issue could be?