We run Server 2016's only but get that same license message since ~ January 2020 only. We have Ncomputing L300 terminals behind. We use CAL per device with Workgroup only and our RDL diagnosers says there are no issues. Each server is its own licensing
server too.
Through gpedit.msc I switched off licensing messages but that has no effect.
Sometimes the terminals get disconnected for ~30 seconds but they come back in the last state, just irritating.
We don't want to give our students admin login rights.