If you can see your character but not the background it's usually because the user downloaded FH+ since it doesn't have the maps required to play the game normally.
If you spawn in a map that you do not possess, you get this black abyss usually, but it can also in some cases be because the location you installed the game to, but also maybe a broken installer.
What I'd advise you would be to remove your game folder(placed in C:\FeralHeart), make sure you remove this completely. Once that is done, download the game again by clicking the download link on top for the regular game having the "Game setup" next to it and then just install the game to your computer again.
If the errors still occur when you log on with the new game installed, try "Reset home" button and then "Go home". It should help.
However, does the start screen of the game work? Do you see the world behind the menu buttons or is that black too?