Campaign level doesn't end

[Idlit]

I am playing the Conquer the world - Alexander the Great Campaign. I am battling the Greeks and the objective was first to get Blue to join me (done) and then to defeat the Green (Greeks). The greeks have now been successfully defeated, but the game keeps on running. My only option is to resign. If I click the "objectives" button I get the "get the blue to join" message again. How do I fix this?