When running pmrun or pmksh it fails with:
pmmasterd: 5033 Cannot resolve hostname
Request rejected by pmmasterd
In the case where this was issue was seen "pmhostlicense -sfh <hostname>" was showing that the client was bound to a different hostname. This was due to the hostname having been accidentally changed to "=" and because the "thishost_" setting was configured in the pm.settings file the masters were trying lookup an illegal hostname for the pmlocald connection.