As I’m writing more PowerShell (what I really mean is googling PowerShell or asking Steven @StevenMurawski), I ran into this weird thing. I was trying to hit an Azure Function that I wrote using Invoke-RestMethod and I kept getting the error:
Invoke-RestMethod : The underlying connection was closed: An unexpected error occurred on a send
WTF????? After googling a bunch, turns out this is a TLS issue. PowerShell defaults to TLS1, I needed mine to be at TLS1.2. More googling gave the the fix. Add this before you make your Invoke-RestMethod call
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls -bor [Net.SecurityProtocolType]::Tls11 -bor [Net.SecurityProtocolType]::Tls12
I’m sure i’m gonna run into this again so sticking this in my blog so I’ll find it quickly 
Even i faced the same issue.
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
is worked for me in my local system. But not in VM.
Tried :
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Ssl3, [Net.SecurityProtocolType]::Tls, [Net.SecurityProtocolType]::Tls11, [Net.SecurityProtocolType]::Tls12
$code = @”
public class SSLHandler
{
public static System.Net.Security.RemoteCertificateValidationCallback GetSSLHandler()
{
return new System.Net.Security.RemoteCertificateValidationCallback((sender, certificate, chain, policyErrors) => { return true; });
}
}
“@
#compile the class
Add-Type -TypeDefinition $code
#disable checks using new class
[System.Net.ServicePointManager]::ServerCertificateValidationCallback = [SSLHandler]::GetSSLHandler()
try{
invoke-restmethod -uri $url -method GET
}
catch{
}
finally{
#enable checks again
[System.Net.ServicePointManager]::ServerCertificateValidationCallback = $null
}
This one also not worked….
finally enabled the firewall on the respective VM which worked for me.