java moss doesnt grow

Is it badly shaded? The only way to really kill it is to accidentally let it float off of wood, or if its shaded.

For me, java moss grows the best the more I neglect it. I would make sure its loose, not balled up or the middle dies off, and stick it in a place that gets some water movement. Forget about it for several weeks. You should see new growth eventually. If you have enough, break it up and place it in several spots in your aquarium. You may find it's happier in some places than others.

Way you attached it and keeping debris off it helps a lot

I had same problem w/JM while other plants did fine. I have noticed as many others have that JM gets most of its nutrients from the water column. The original plants appear to die and leaves turn black but new plants start to develop from these blackened leaves. I take these new plants and put in gravel. These new plants then grow fine.