Trouble installing heavensward. Please help

So, I got the Windows version of ARR installed and today i bought heavensward, which too was the Windows version, but when I try to install it, it says base game is required. Wtf?! I have the base game and the correct version too, this is starting to get really frustrating and any help would be greatly appreciated.

I also registered my heavensward code in mogstation and it said it was successfull and whatever and that it was the Windows version of the game.

Edit: I booted up ARR and a window popped up which started a 4 gig download. Not sure if i get to play Heavensward once its done downloading but i'll edit my post again if my troubles aren't solved.

Edit2: Downloaded the patch and my ARR became Heavensward. Problem solved! Question remains though: What the hell is the disk for then?

My problem is solved, lock this thread please!

Seeing from your edit it might be necessary to patch ARR to patch 2.55 before installing Heavensward but I'm not 100% sure

Could be, except that i've already downloaded the 2.55 patch, completed main story too. When heavensward early access was launched i downloaded 4 gig patch the night all worlds were on maintenance. I've been fully able to play ARR until now, so not sure what's the problem here. But let's hope i'll get it working after the dl.

Edit: Oh, btw, it says "Downloading: ex1"