I don't have much expertise on orion, But below are my suggetions
(You might have already carried below steps, if not try these)
1. Check any connectivity issue: ping the 3rd stack to see if you have ICMP access
2. Someties copy and paste of text, could add a "mysterious" space in the string, so it is better to add the strings manually (snmp config)
3. Network could be running slowly, try increasing the SNMP Timeout.
4. re-run the configuration wizard
5. stop & re-start all services & see if problem goes away.