probably communication issue? check if host and port where message server resides is availble from pc where you start IRd from (since you seem to be able to connect to the rest of genesys servers probably TCP-port is the issue).
and do you use a dedicated message server for strategy monitoring?
Just have a closer look to the newest ReleaseNotes of IRD 7.6.
It had something to do with the order of the IRD-Connections in CME (If the DAP was added before the MessageServer was than the result might be a connection problem).