hmmm..
Not sure if there is any info in FAQ 3.5 that might help. I guess the trouble is that Ubuntu may not be an officially supported OS for OMSA. It's possible with a web search other folks have gotten Ubuntu + OMSA working, but something is clearly up with your setup since the troubleshooting tool can't see the OMSA version in the SNMP test. Is the OMSA service running ok on the Ubuntu box?
Rob