You may get the following error in ECP:

500 Unexpected Error :(  - An error occurred and your request couldn’t be completed. Please try again.

 

and 

 

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'.

 

Resolution:

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.

 

Prabhat Nigam

Microsoft MVP | Exchange Server

CTO @ Golden Five Consulting.