Oh you did! Indeed, you have to complete the human campaign all the way through (to the point that you get an epilogue) to even be able to start the 2nd largest storyline after the human things.

Endless sky follows the old and storied tradition where 90% of the game’s content is locked behind speaking to a specific random NPC near the starting town, and not giving any hints at all that you’re going the wrong way. You probably fell victim to that.