You can get this error while trying to open an RDP session.
An authentication error has occurred. The function requested is not supported
This is due to a combination of three factors:
- You activated NLA on your target computer
- The target computer is not patched for CVE-2018-0886
- You enforced the Force updated clients or Mitigated parameters on the source computer
Choose one of the following and see links in the More about section below if you don’t know how to do it.
- Disable NLA on your target computer (Not recommended)
- Patch your target computer for CVE-2018-0886 (Recommended)
- Enforced the Vulnerable parameter on the source computer (Not recommended)