If a user is logged into multiple sessions within the same browser, it can cause pages such as the Admin Hub to not load due to Work 365 using Azure AD for authentication.
To remedy this, go to "Billing Contracts", select a billing contract, then click on the Work 365 button. This will force a user log in.
To remedy this, go to "Billing Contracts",
Select a billing contract, then click on the Work 365 button. This will force a user log in.