I ended up purchasing a valid copy of Microsoft Office 2016 Pro Plus from a (sealed) Microsoft USB key. Once installed the product validated. I then had the MS Office 2016 was checked out by Microsoft and MS confirmed it was legit as I had purchased it from a eBay seller (~2650+ - 100 percent positive feedback) I just wanted to make certain it was legit copy as there's copies of MS Office being illegally sold on eBay that aren't legit)

First nninstalled all copies of Microsoft Office and then installed Microsoft Office 2016 Pro Plus and now everything is ok.

Note: If you have other versions of Microsoft Office Installation installed on you PC. The Microsoft Office installer won't uninstall them and one or installations may interfere with the current installation. So it's better to uninstall all versions when installing a new version as to have two or more versions installed potentially causes problems.