Can't trade for corporation's resources ("You must be joking")

[dividertabs]

Previously, whenever I've founded a corporation, I was able to trade for as much of that corp's resources as I wanted. But in my latest game, I've popped a Great Merchant able to incorporate either Cereal or Sushi. I saved just before founding the corporation, and no matter which I found, none of the AIs will trade any of the resources that the corp wants. In the diplomacy screen I see they have plenty of the resource (as many as 6), and the corporate logo appears when I mouse over it, but it is red with the ever-unhelpful "Surely, you must be joking...." This happens even with Pleased leaders.

Are there any other requirements to trade that I could be missing?

 

[beestar]

That's the same message you get if you don't found the corp - you've already got a fish, why would you want a second?

I've found that if you wait 1 or 2 turns, some flag trips (the AI "realizes" that you have the corp?), and then you can get that second fish.

 

[dividertabs]

Thanks; I'll wait a few turns and see what happens.