Enterprise Manager

I have upgraded our OEM from 11g to 12c Cloud Control using the two system method. I am in process of deploying/configuring agents using the Enterprise Manager 12c Upgrade Console. I have encountered one agent in which the deployment has reportedly completed successfully but the Health Check shows the ping test failed and I don't understand why. I have found some information suggesting looking at the emd.properties and the gcagent.log file but I see no errors listed or indication there that anything is amiss. The os on the target is
Linux 2.6.9-42.EL #1 Wed Jul 12 23:15:20 EDT 2006 x86_64 x86_64 x86_64 GNU/Linux
the RDBMS version is 9.2.0.8.0 and the existing agent is 10.2.0.4.0., I don't know if that matters.
I don't believe it is a firewall issue as I have the proper ports open in both directions. I am not clear where to look or what to change to resolve this issue and be able to switch over. As far as I know the agent has been reconfigured from unsecure to secure or vice versa since the backup of the initial repository was made and I'm not sure how to proceed with that quesiton. One note I found appears to suggest unsecuring and resecuring the console but it isn't clear if they are suggesting the old or new console. There is some confusion as well as to whther they are referring to the agent or the console as well. Please help me resolve this problem.

Thank you.
Bill Wagman