Can’t connect to Visual Studio Online from any version of in VS: "The underlying connection was closed: An unexpected error occurred on a send."

Interesting one today.   PROBLEMCustomer reported not being able to connect to VSO from any VS version. Kept getting this: The server returned the following error: TF400324: Team Foundation services are not available from server <ACCOUNT>.visualstudio.com\DefaultCollection. Technical information (for administrator):  The underlying connection was closed: An unexpected error occurred on a send. TROUBLESHOOTING The customer…

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