Migration Manager connectivity to Office 365 failure - PSremote errors on synchronizing mailboxes to O365 (4258233)

Microsoft have retired the URI  “https://ps.outlook.com/powershell “  and advised to reference https://outlook.office365.com/powershell-liveid.

Microsoft is deploying a fix to the tenants, but some products globally are still experiencing issues with Remote Powershell connectivity. 

Resolution 1:

For the PowerShell connection issue this was caused by a recent upgrade to the Office 365 backend servers that caused this issue to happen, Microsoft has rolled back these changes and this issue should not be seen any longer. If you are still experiencing this issue on any of your servers please follow the below steps that have been provided by Microsoft.

1.  Close off the existing PowerShell session.
2.  Use the clear cookies registry option (at least) once: REG DELETE "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\WSMAN\Client\ConnectionCookies" /f  
3.  Start a new PowerShell session and try again. 

AS Explained here: https://support.quest.com/kb/235186

Quest does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 “Description of the Microsoft Windows registry” at Microsoft Support.

Resolution 2:

Install Windows Management Framework version 5  on Agent hosts, and Consoles for Migration Manager  https://www.microsoft.com/en-us/download/details.aspx?id=50395

We have found that if the fix from MS hasn’t been deployed out to a tenant, the above install “Resolution 2” will resolve the issue.

ALSO - It is a good practice to run Resolution 1 even after the fix from MS is deployed.