No matter what key I assign to it, I can return to base. Instead I get the Communications pop-up. Very annoying because now I can't even finish a mission? How do I solve this?

No one?

I believe you are confusing the communications command Return to Base (which is used to tell your wingman to return to base [which explains why you get the comms pop-up]), with the Enter Subspace command (Alt-J), which will end a mission.

same problem. alt j doesnt work, just brings up wingman command.

Same here, I noticed by default the game has shift-J. I tried binding the return to base to 'P' and still the comms panel pops up.

Really cannot play the game.

This happens in all training, C, B, and A, which I have completed the objectives, then had to press Skip Training to move on beyond the training.

I completed the first mission objective, then was left stranded because I cannot return to base.

You guys are using LEFT ALT, though, right? Haven't run into any issues like the one you guys are describing.