MS Office 365 Unknown Error 0xD0000019

I'm trying to activate Office 365 (university edition) on my iMac iOS 10.13.3. It get up to the password verification and I get the Unknown Error window with this strange error code. I need Office 365 to be compatible with my students.
I have spent over 3 hours on the phone with Microsoft Help, where we twice uninstalled Office 365 and reinstalled. The error code remained.

I have spent several days corresponding with my university's IT department and they can't reproduce the problem.

I have reinstalled the OS

I can only assume that something in my system is interfering with it, such as a rogue font.

Any suggestions about where to go from here?