Did you put grayscale while you were making the height map? You should re-read the feralheart manul and/or you can 1.delete file, 2. Uninstall feralheart, 3. Reinstall feralheart and 4.remake your map (note: before installing feralheart, it would be wise to move the feralheart files you want to keep in a different folder and then after you are done installing feralheart, you may put the files you keypad and removed them back where they need to be at in the feralheart folder)