If I understand tour problem correctly, it's just the item.cfj; if you have a pack that differs from other users the items might not show up. So there's not really any fixing it. You would have to download the packs that they have. Sorry, if I misunderstood your question.
Edit: D'oh, I was ninja'd, lol
It could be possible that they can see items, but different ones that you have. If they have a different item pack than you that could be it.
If you can see all the items in the pack that you downloaded then you, in fact, did it correctly. It's the matter that others may not have the same exact item pack than you do. Since FH only reads the codes in the order that they are placed in the item.cfg and not the code itself, so it won't recognize an item if it's in a different placement. [If that makes sense.]
If I understand tour problem correctly, it's just the item.cfj; if you have a pack that differs from other users the items might not show up. So there's not really any fixing it. You would have to download the packs that they have. Sorry, if I misunderstood your question.
Edit: D'oh, I was ninja'd, lol
Just like what Starry and Owly said... anyway, if you're looking for a good item pack that most people have, I would recommend the Pawesome Item Pack V5. This is one of the most popular item packs, since it combines like, 50 different item packs into one, and you'll have items in common with more people, so you'll be able to see more. Hope this helps in some way.
Try following the tutorial I will link below and see if it helps. ^^ It may just be all the meshes and stuff being misplaced, not a worry dear c:
Tutorial: >>Click Me<< (http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=45115.msg620625#msg620625)
~ Whisper
Seems there are many floofs who helped out in this thread. Let me know if any of the solutions they sent you helped you with your issue so I may ask a Mod to lock this thread. ^^