As of this patch, conversion quests do not allow two of a single agent. This was allowed previously, and nothing in patch notes appeared to identify this change. If you have 3+ of one agent, you cannot use two of them in a single conversion. Thread that looked similar but I didn't think was: https://forums.daybreakgames.com/eq...ncommon-conversion-removes-duplicates.264583/
You must be trying to convert 2 of the same iconic, that's never been possible. I've converted 2 of the same non-iconic since the patch, so nothing has changed.
Works on common agents but not any higher ranks. Would be useful to understand if that is intended or a bug.
I would put it in the realm of being an intended bug. Once any instance of an iconic agent is used, none of the other instances can be used (for anything -- even combining). Multiple non-iconic uncommon agents should be used individually, as well as regular common agents, but that's about it.
And half of uncommon agents are also not iconic. With this setup, it seems that duplicates of iconic agents (x2 and up) are useless, and should be converted up whenever you get the chance. I'm not sure what you do with duplicate elite iconics.
you [release] them from their duties and get experience for a category, 2 agents of the next lower quality.