I just finished upgrading our "test" environment from 9.14 to 9.20 and everything seems to be running okay, the only issues I just ran into this very particular issue.
I can login to the Desktop Workbench without an issue but when I try to edit a user I get the following error: The HP Project Management server is down or unreachable. Please contact your HP Project and Portfolio Management system administrator. (KNTA-10035) the full error is attached.
I have tested opening the workbench from the site and editing a user and was able to do that without an issue, I have also tested opening the workbench from a different computer without issues as well.
(Prod and Dev are working fine without an issue even though they are 9.14)