Powershell test connection fails at "Session Initialized". By hovering over the "X", you can see more details of the error:
"Test connection failed with the following message: System.Exception: Could not establish PowerShell session for end point Microsoft.Exchange @ PowerShell endpoint XXXXXXXXXX powershell using Authentication type: Basic, User: Administrator, using service credentials: False, ViewEntireForest enabled: False. New-PSSession : Connecting to remote server XXXXXXX failed with the following error message:
[ClientAccessServers=EXCH,BackEndServers=,Requestid=XXXXXXXXXXXXX, TimeStamp=X/X/X] Access is denied. "
This error can be caused by several things including the Administrator account being entered incorrectly, basic authentication not being enabled in the Exchange server on IIS for the PowerShell authentication feature, or the roles not being set correctly
Enter the Powershell URL into a web browser (on your ACC if you have configured Powershell to go through ACC) and when prompted for Username and password, enter the credentials. The next page should be blank with no errors. If there are any errors then you are using the wrong username and password. In some cases, you may have to add the domain to the front of the username.
Go into IIS on your Exchange Server, open the PowerShell directory and select the “Authentication” feature. Enable basic authentication and test to see if this has fixed the error.
Additionally, make sure the the relevant roles are added to the Administrator account: Mail Recipients, Organization Client Access, and Recipient Policies. This account also must be a domain account.