Using Classic Outlook on Windows for personal email, calendar, and contact management
Just to add to this as well that today we've started getting users that are already logged on getting Outlook flashing when trying to retrieve data but again bouncing them onto a different server seems to fix it and it's not linked to a certain server so for example user A can be on server A with the problem and we bounce them onto Server B and it all works whereas User B could be on Server B and get the problem so we bounce them onto Server A and this fixes it. I've also tried to setup 2 new users in Outlook and both are now showing "advanced setup" when it should pick up their settings and log on even though we've got SSO enabled and then they error so it's getting worse every day.
It still seems that the Volume Licence version of Outlook we installed to test still works though so it does appear linked to the Click to Run version, not sure if anyone else has a Volume Licence edition they can test this theory with just in case it's not relevant ?