When I try to perform the top row action "produce", I get the message: "This will have no effect. Are you sure you want to continue?"
Why?
When I do hit continue, indeed: nothing happens.
What can cause this? It's really ruined this game.

Do you have enough power/popularity/gold to pay for the Produce action (depending on how many workers you have)? And are your workers in hexes that can produce resources?