Check if you are exporting all thre props (head, neck and body) for the final OBJ. I kept trying other settings and managed to get the Janim FBM working, first are the settings I used to export the V2 body and on the bottom are the settings I used to export the final props, these are the results I got, the neck is a little weird and when I bend the body some seams get separated, I think it has something to do with the weld body parts settings. Anyways keep trying you'll get it soon :)