Office365 blank screen on login attempt

Office 365 (2016 64 bit) version 1802 (Build 9029.2167) on Windows 7 home premium SP1, updated recently.

After a repair install of Windows 7 (here, needed to repair Office 365 (second repair option required) as no Office app would start.
Office fixed, would not activate (blank screen after 'sign-in' and entering email).
Two accounts linked, removed account with subscription, office activated. Tried to add other account back in, blank screen.
Uninstalled Office. Reinstall office. Office is activated, but same thing when trying to add other account back in.


Any ideas?

Yes, two user accounts, both are Microsoft accounts. One is linked to the 365 subscription, the other is not. Both were showing up in Office prior to the repair install.
Now, the non-subscribed account is linked to the Office install, and the other is not. When I try to add the account, I get the blank window after the first logon window (enter the email).

Yes, rebooted.
Yes, both accounts are active

Trying the same thing on another PC (connect both accounts), I get a verification screen instead of a blank screen.
Both accounts have 2-step verification turned on.
I can log into either account on the affected PC using 2-step verification, just not from any Office app.