Users are not able to connect randomly. In RDS License Manager, reviewing the configuration results in "The system cannot determine if the license server is registered as service connection point(SCP) in Active Directory Domain Services(AD DS) because the AD DS cannot be contacted.
Then all of a sudden it goes away. The RDS server and the domain controller are both VMs running in Hyper-V connected to the same virtual switch. The DC is the primary DNS server for the RDS server. At the time of the issue, the DC is able to be pinged with no problem. Also, there are no entries in the logs on the DC that indicate a problem with AD or DNS.
I've attached two screen grabs, one that shows the issue, and the other that shows no problem, both of which happen at random as far as I can tell.
When I looked into this, I noticed that the secondary DNS server of the DC was set to the ISP's public DNS. I removed this as suggested by a comment in this post: https://social.technet.microsoft.com/Forums/office/en-US/4061ae7b-b692-4df4-bcca-95a7c8c86330/gpupdate-fails-event-id-1054-windows-could-not-obtain-the-name-of-a-domain-controller?forum=winserverGP.
We'll see if it makes a difference. In the meantime, suggestions are still welcome and appreciated.