Hi I started the campaign with historical D-day and I try to drop the paras at their pre set historical hex but the game says it is an invalid airdrop hex, how can this happen?
I don't know what actions you have done yet, but the first thing i would do is make sure you have clicked the 'invade' button for each of your invasion task forces. Paradrops cannot occur except adjacent to an invasion hex, and they won't fly unless the invasion is launched.