I do not have any shared mailboxes, so that isn't it.
Also, I verified that I do not have any other versions of Microsoft office installed, just a single instance of Microsoft 365 Office apps for Enterprise.
One thing I was thinking about was licensing, as it didn't seem to be connecting to allow use. I did download and run the SARA tool and used the option for “Fixes Office subscription activation issues”. This stripped out the licensing information and upon completion and reboot, required me to re-activate the license for my machine (we use an enterprise license, through email address option).
It 'seems' to be working now but I thought it was fixed previously and then started up again so I wont know for a little while.
Fingers crossed