You are not installing the maps properly.
The download is either an .exe or .zip.
The .exe installs the maps to C:\FeralHeart by standard, if it doesn't work then "you" changed where the game was installed, and in that case "you" must correct the original install path.
The .zip is an archive of the files and "you" yourself must install the maps into the game folders, I did include instructions inside of the zip archive of how you install the mods and maps.
Always double check how you install the maps since if you do it the wrong way the game will not find the maps.