Note that my role is Primary admin. I do not know about Master admin.

I use Mozilla Firefox. In Private browsing, there is no change: same error when deleting user, same busy icon when displaying Role in Edit User.

Using Chrome in Incognito mode, same behavior.

In Firefox, I deleted all Intuit cookies, quit Firefox, restarted and logged into Quickbooks. Same behavior.
In Firefox, I turned off Enhanced Tracking Protection for intuit.com and app.qbo.intuit.com . Quit Firefox, restarted, same behavior.

Very frustrating.