Enter,Ctrl and Shift keys did not work
My situation was resolved by not installing a Office 2016 application.
OS Windows 10 ver 1903 x64
viewer 6.10
host 6.10
OfficePro Plus 2016 15.0.4446 x64 (Click-To-Run)
Ending Tasks did not produce any solution so I built a second system and tested at each install.
OfficePro Plus 2016 Click-To-Run was the repeated problem.
By default Word. Excel ,Access, Outlook .Onenote ,Powerpoint, Publisher, Skype for business and Onedrive for business are installed.
Uninstalling Office and reinstalling without OneDrive for busness repetedly solved the problem.
I did have issues with OneNote but that was a non repeatable result.