Isiac.T

I have successfully docked onto my moon lander in a low orbit above the Mun for a refueling, since I am on career mode I only have access to the Clamp-O-Tron Jr. I attached an FL-T400 fuel tank to a clampotron and my Mod key+Right click is not pulling up the fuel exchange window! I have tried it with and without a adapter, and they have no effect. It shows that the ships have docked and become one, but no fuel transfer window. Help!