Hey Kattasmith you have to read what it says on the FeralHeart+ download section (at least I think this is what you're going through cause I went through this same problem yesterday with the same error message). If you are planning to play it you first have to get your character in Bonfire on the regular version of FeralHeart and set Bonfire as the home since the Lonely Cave is not in FeralHeart+. Once you do that the game should work without the black screen. Just make sure that whatever characters you are going to use in FH+ have their home set as Bonfire or Ficho etc and are in one of the regular default maps because if they are in any of the Atlantis, South Pole, SkysRim, or any other of the newer maps on regular FH when you switch to FH+ you'll be in the blackness. I hope it works for you.