I have the Elite Dangerous Legendary edition I just started game and in starport services it says I need Horizons I thought when the game installed it was with Horizons included?
If it is the physical copy there should be a code in the case. If it is the digital one check your add-ons and make sure it shows Horizons is installed.
You need to go to the playstation store, in the menu look at the bottom for redeem codes, look in the box for the code, enter it. Then it shoud be atomatic from then on.
