Well...first your going to need to do something with your tank, because java fern could be put in a dark closet for 4 months and still survive. I don't want to scare you away from plants, so lets find out what's happening.
Haha don't feel bad. I have a particular tank that doesn't grow Java fern, Anubias, Anacharis nor any moss variety I've tried (several) also isnt any of my swords favorite place either (they take forever to finally get going) but it'll grow crypts of any variety I've tried like no body's business. But the rest of my lower light tanks I can hardly keep up with those plants lol. Except Anacharis I cannot grow Anacharis here for anything, before I moved here Anacharis was like a really really annoying weed that I could NOT keep up with.
Different tanks different issues lol.
Try something like Anubias or Anacharis both are pretty easy and inexpensive and hardy.
I wouldn't worry about not being able to grow java fern, I can't grow it in any of my tanks! It always dies! I can grow stuff like anubias, dwarf hairgrass, subwassertang, ricca, java Moss and such just fine though. Oh, and don't get me started on anacharis, I'm trimming ten feet a week of that stuff! I started with a bunch for 2.99 from Petco, and now I just have way too much. It's awesome stuff for sucking up nitrates and even ammonia, so I do highly recommend it.