Can't join CG?

So I have never touched Powerplay, but I have been a part of several CGs. Tonight I decided I would finally give Powerplay a go and try out the CG. I signed up for Edmund Mahon and flew to Horizon's Glow in Col 359 Sector DZ-M b9-2 to sign up for the Alliance Campaign. However, no matter how many times I click sign up, it doesn't show me as signed up for the CG. Even logging out and logging back in doesn't change this. Just to see, I went out and did a couple basic reinforcement actions in Col 359 Sector MR-T C4-8 (a Mahon reinforcement system marked on the galaxy map) and got no credit for the CG.

Has anyone else had this problem? Am I missing something obvious?