What program are you using for the height map? Programs like SAI and Paint don't have a greyscale option, therefor it may not work.
Also, make sure the map is 513 x 513 and saved as a .png file! If it's not the game will crash.
Lastly, the layers (if you used them) must be merged.
Also, make sure you followed everything here: Click me (http://www.feral-heart.com/index.php?option=com_content&view=article&id=6&Itemid=11)
Mocha, you beat me! |D
I got it to work! Yes I was using SAI but I also have photoshop so I could fix it, it has just been a while since I've made a map I forgot heh, thank you guys <3
Ah yus, programs like SAI don't have the 'greyscale' and 'RBG' color options needed for maps. I use Photoshop for maps of FH because of that. You could set the file to greyscale on PS and save it as the photoshop file and then open it with SAI because SAI can open Photoshop's files. I do that a lot.
Good luck with your map! <3