I don't believe it's the export folder.
It appears to be that something has gone wrong...FH can't locate what it needs to load the default terrain, so, you need to backup any maps or presets you made (by moving files out of FH folder to somewhere else) and uninstall FH, delete the FH folder, and then download "Feral Heart Game Setup" Yes, you already have it, but it's possible to get a broken installer, so I'd redownload it, just in case. Then make sure to install the one you just downloaded, and see if it works.
Hope this helped. ^^