Hi Joe,
I’d like to confirm whether the users receive the message “Setting up Exchange Online... this may take a few minutes” in the Microsoft Office 365 portal. If yes, this issue occurs if the services hasn’t finished provisioning for the users. It may take up to 24 hours to configure and provision Online Services. Please wait for more hours, and let me know if the issue persists after 24 hours.
Meanwhile, I suggest you check whether the uses’ mailboxes has appeared in EAC (Exchange admin center).
Thanks,
August Sun