I installed KB4580346 yesterday evening, and restarted the server as directed.
After the restart, the PCs here could no longer connect to the server with the Dashboard Connector under the Windows Essentials Experience.
I am able to connect to the server through the network folder and login information.
Upon opening the Windows Server Essentials Dashboard, no user accounts are shown, and the "Add a user account", an error pops up "Window Servers Essentials: The task "Add User Account" did not complete successfully.
An error also pops up "Health Alert Error: Alert Notifications are not available for Health Monitoring due to an error or incomplete action, or service has stopped working. If the problem persists, contact that person who administers your server."
I tried rebooting the server again, which did not fix the problem. I also rebooted one of the PCs on the network which also did not repair the problem. I then uninstalled, downloaded and and reinstalled the Connector software to which also did not repair the problem. The error persisted "Cannot connect so server" and the Dashboard connector box remains gray instead of green.
Seems some of these updates do more HARM than good.
Update:
I uninstalled KB4580346 and the user accounts were restored in Windows Server Essentials Dashboard.
I also found and downloaded the wushowhide.diagcab tool and installed it to hide KB4580346 which is apparently bug ridden.
It would seem only fair that if customers are going to be used as Guinea pigs than we should be able to bill Microsoft and get paid for the HOURS lost chasing down problems that their poor and obviously not thoroughly vetted updates cause!