Howdy SharePoint admins !
I am writing this blog because it wasted about an hour of my time trying to find a fix for it. Installed SharePoint 2016 - Mar 2018 CU and then I tried to run the PSConfigUI.exe.
It does not come up. I click again and now it throws me the error "Only one copy of the SharePoint Products Configuration Wizard can be run at a time."
Hmm.. Tried to look at the event logs.. nothing there. Looked at ULS, nothing there..
Tried to restart the SP Timer Service and the service would not even stop. I was left scratching SQL instance.
Hope it helps someone out there.