Invoke-WebRequest : The underlying connection was closed: An unexpected error occurred on a send


when Testing the Hybrid Connectivity using the below Command,

Test-HybridConnectivity testO365Endpoints

It is failing with the following error,


It is all because TLS, TLS 1.1 and TLS 1.2 not allowed in the server, Which is why the command failed, To resolve the issue, do the following,

Open the Command prompt and run the below command,

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

Once the command has completed, Do run the command and validate

You can see it has been completed without any issues.