This is related directly to the update associated with CVE-2018-0886. More detail can be found in the following post on technet:
You can run get-hotfix from PowerShell to view the updates and if the machine you are on has not been updated or does not include the May update then it is advisable to update to the May 2018 update.
Ensure that your SCCM server or your WSUS server has the latest update to push out to computers and get this installed. Once all comuters have the same update then you can reconnect to your RDP server with success.