The answer is, be sure you know which machine the agent is running on. When you right click the agent in Domino Designer, and select Run, as I did, the agent is not running on the server that the database resides on, but rather inside the Domino Designer client. that is going to be Windows or Linux depending on your workstation.
So why did the one agent work while the other did not? Well the one that worked was activated from a button in the Notes Client, and the function attached to the button used Run on Server
. The server was indeed IBM i. However, in the case of the failing agent, I executed that one from within Domino Designer as mentioned above, thus no DB2 connector.
Here's to hoping someone can learn from my pain!