I got the same result as last time, namely that the verification server was down.
I have just attempted to install it, first by updating to Office 14.7.7, which I could do, then by entering the product key. But occasionally my wife likes to use the laptop on the dining-room table, where she can spread papers out, and she is used to MS Word. After installing Sierra (10.12.6) on my 2010 13' MacBook Pro, I didn't bother to install MS Office.