Problem statement
The users are added as Tenant Admins and can be verified from the Dashboard > Settings > Tenant Members, but when they try to log into the dashboard, they cannot log in. After accepting their invitation emails, they are still prompted to log in but are not able to proceed past the login screen.
Troubleshooting
Check if the Account associated with the tenant has the Teams feature enabled and if the user facing the issue is added to the Teams account.
Cause
If the tenant is part of a Team, even though a user is a tenant admin, to access their tenant, the user has to be a member of the Team as a Team Contributor. The Team Owner should be able to invite these users as Team Contributors .
Solution
Once the user accepts the invite and is a member of the Team, they will be able to access the tenant. The Team Owner can also grant them access to other tenants from the Teams Dashboard by clicking on the Team member and assigning more tenants.
You can find more information on Team member management by reviewing the following document: Team Member Management