Exchange 2016 Hybrid Wizard Fails to validate Domains.

 You are running the Exchange Hybrid Configuration Wizard (HCW) and it gets stuck at validating domains.  You try-

Set-FederatedOrganizationIdentifier -DelegationFederationTrust "Microsoft Federation Gateway" -AccountNamespace "MYDOMAIN" -Enabled $true"

You get- An error occured while attempting to provision exchange with the partner sts.

Add the following registry keys and reboot.

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft.NETFramework\v4.0.30319]
"SystemDefaultTlsVersions"=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft.NETFramework\v4.0.30319]
"SystemDefaultTlsVersions"=dword:00000001

Go into EAC, organization, remove the federation.  Re-add it, add your domains, set your TXT records.  Verify they are there with NSLookup, click Update.  Re-run the hybrid wizard.