You may get the following error in ECP:
500 Unexpected Error :( - An error occurred and your request couldn’t be completed. Please try again.
The following error in the event viewer event id 4
Unable to determine the installed file version from the registry key 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PowerShell\1\PowerShellEngine'.
This is a PowerShell registry key of Exchange 2016 CU1 server. In case you remove corrupt the regitry Key you can download and import it.
IMP: Make sure to backup your current registry key.
Microsoft MVP | Exchange Server
CTO @ Golden Five Consulting.