I felt a bit stupid today! I was trying to upgrade Microsoft Office on my PC from Office 2016 to the latest and greatest version that comes with our Microsoft 365 subscription. So I uninstalled Office 2016 and ran the installer from office.com and it was a very easy install.
But when I opened my newly installed Outlook it looked just like the version I had been using before. I looked at the version in “About Outlook” (in File > Account) and started to get confused, my subscription still said Office 2016.
After reinstalling another couple of times and a bit of Googling it turns out that Office 2016, 2019 and 365 all share the same version number and even build numbers, and the version that actually gets installed depends on the product key which you have installed. And on top of that, uninstalling Office doesn’t necessarily remove the product key.
To fix it I had to run a VBScript file from the command prompt. You can see the product key and version which you have by running this:
cscript "C:\Program Files\Microsoft Office\Office16\ospp.vbs" /dstatus
And then you can remove your Product Key by running this (you’ll need to be Administrator):
cscript "C:\Program Files\Microsoft Office\Office16\ospp.vbs" /unpkey:XXXXX
Where XXXXX above is the last 5 characters of the product key which you found in the first command. After running this I was then able to run the installer again, install Office again, and this time when I logged in with my MS365 account it activated my Office 365 subscription.
Thanks to jreynolds1030 for posting the fix on the Microsoft Answers site.