SSO login issues
Once SSO is set up users can login by authenticating via Microsoft Account.
With SSO enabled the access to Clearooms is controlled from your own Office 365, usually (but not always) via Group policies.
If you have a user that sees this message (see screen shot) this is due to them not having the correct access, often this is due to them not being in the correct group in Office 365 within the active directory.