This could be due to CredSSP encryption oracle remidiation

24 May

A quick fix when connecting to an unpatched Server 2012 R2 via RDP from a recently patched Windows 10 workstation.

Navigate to: Computer Configuration > Administrative Templates > system > Credentials Delegation > Encryption Oracle Remediation.

Edit the local policy and set “Encryption Oracle Remediation” to “Vulnerable”.

This is just a quick fix, obviously, you should get everything patched ASAP and set this back to “Not Configured”.