The TAG does not cover the fact that licenses need to be copied to both the primary and secondary master node with HA enabled. In my mind, this should ideally be covered in the "License handling" chapter, as well as a step in the configuration instructions for HA.
This is mentioned under "License handling", in the Note-box under "Location and format of license files". > Note > > When running VSM Server in a high availability setup (see High availability), > license files should be copied to /opt/thinlinc/etc/licenses on both nodes. However, it is not mentioned under the HA instructions.