Microsoft Office shows a yellow bar at the top saying: "Product Notice. There was a problem checking this devices license status. Please sign in with the Office 365 account this device was activated with."
You will try to log in and it will keep the top yellow bar. Regardless of reinstalling Office, the error will persist.
Close any open office products
Run cmd as admin
cd C:\program files\Microsoft office\office16 (or program files (x86), whatever's relevant)
type in: cscript ospp.vbs /dstatus
this generates a list of all the license keys install on your pc. You want to look at the last line of each paragraph: "Last 5 characters of installed product key: *****"
type in: cscript ospp.vbs /unpkey:***** (whatever those 5 chars where). repeat this for every license key installed.
Once they've all been removed. Open an office program, sign back in and you're done