Custom Monitor Issue

Hi

I have custom monitor that test mailq size. I have tested the the SNMP with the following command from the server: snmpwalk -Os -c PASS -v 1 HOST .1.3.6.1.4.1.2021.8.1.101.

That works fine. But when I test the monitor I get: The Monitor did not respond to the test request

The Opmanager is running on Linux.

Thanks in advace.

Ryan