According to your information above, you are using O365 and encounter the OWA repeating redirects error.
Do other users in your organization have the same issue and did you have this issue before?
What role is assigned to this account?
I see some similar issue was caused by admin roles you mentioned above, and you could try removing all roles for this account firstly then reassign the role back to see if any help.
This thread discussed the similar issue: Error 500: Repeating redirects detected - Outlook Online
Click ‘Manage roles’ under the heading ‘Roles’
Remove all admin roles other than ‘Global Administrator’ and click ‘Save changes’
And if the solution above is not able to solve your problem, the issue may be related to o365 backend. Here we could open a service request to o365 backend to check what may cause this issue. Get support
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