In order to play on both PC and PS4, you will need to purchase licenses for both PC and PS4, and register them to the same account. That goes for the base game (A Realm Reborn) and any expansions (so, currently just Heavensward, but come next summer, Stormblood as well). If your account only has the PC license, the game will only work on a PC.
When you bought your PS4 version, did you register the product key to the same account that you are using currently to play your free trial?
