2 month Activated Office 2016 ProPlus started to loop the question for activation

I am having an activation Issue on one of our Office Computers with a Office 2016 Pro installation. It claims it will deactivate in 4 days on startup of any Office App (except MS Project) while in the Office account it tells me the Product is licensed and activated. The 4 day counter doesn't even count down it says that every day and there are no limitations in usage of any Office App and it is the only Computer of three doing that with the same setup running. Also Office ran now on this device for 2 months without a complaint.

I searched now for a full day on Google trying to figure this out without luck.

What I tried thus far is to do a quick repair,

a online repair,

reinstalling,

deleting the whole office installation with a Microsoft tool killing out all settings and deleting all traces of office and then reinstalled everything,

Looked up for Office OEM keys inside the registry (that where not there),

started Office as an Admin and tried activating it this way.

Looking at it its more annoying than an issue at all since this message keeps remaining the same 4 day counter while remaining fully functional so I hope maybe someone can give me a clue how to get this message out from this computer. Maybe I am just too stupid to google this problem correctly and haven't found the answer that way but I am at my limit of ideas and posts I could find about this issue.

Thanks for everyone who is willing to help us out