Need Help Logging In

So I had to move to Japan for 6 months and I forgot to bring A Realm Reborn. Well when I got Heavenward I got it as a download. Now since I forgot my ARR disc I bought Heavensward to try and play not knowing if it would work. It didn't. When I log into FFXIV on my PS4 (Been playing on my PC for a while) it keeps telling me I already have an existing service account (duh) and if I want to keep it to not proceed in creating a new one. However I have no other option to proceed with my existing account. Could someone point me in the right direction? Thank you!

Wait, so did you already have the disc of A Realm Reborn downloaded on to your PS4?

I did. I forgot it at home and bought Heavensward instead of another ARR.