I opened Word 2016 right clicking and selecting Run as Administrator.
Provided my administrator credential (which is different from the one I usually log into my PC).
Then the embedded Excel sheet worked fine.
Additional information:
Previously I had Office 2013 and the embedded Excel was working with my non-admin account.
I didn't try to repair Office 2016 which I downloaded and installed from the Office 365 portal.
Office version is 64 bit.
Hope this info helps.