Hi, I recently started using Forge and I will say I am new to the whole thing so I may not know a whole lot. I downloaded the Forge 1.6.2 Installer and it worked completely fine on my PC and i downloaded the client and everything. So i downloaded my first mod (Zan's Mini map) and went to my online server and tried using it and it worked perfectly. Then i tried installing the Small Boats Forge mod and i put it in the mod folder and tried using it. I crafted the recipe and I saw the item show up in the crafted box to the right. I tried dragging it into my inventory but every time I tried it would just replace itself back into the crafted box and wouldn't let me put it in my inventory. I couldn't even use it. So I went to single player to try it and it works fine! But every time I try using it on my server it won't work. The mini-map works but the Small Boats mod doesn't? I tried searching for an answer and all i could find were people telling me to create a modded server. So i opened the Forge installer on my mac and clicked "Install Server" and I did everything it told me to and I tried again and nothing! It didn't work. Everything else i find on the subject is just people using Java Script. I don't know anything about that, like I said I'm kind of a Newb when it comes to this. PLEASE HELP!

I'm sorry for responding to a relatively old post, but I have the answer!

 

This behavior happens when the mod is installed (or working) only on the client side, but not on the server. What is happening is your client shows you the crafting recipe (GUIs are client-only), but when you click on it, the server says "Hey! That block doesn't exist, undo what you just did!" (the server handles your inventory).

 

To solve this problem, you need to put another copy of the mod in the server's mod folder and also make sure that the files in the server's config folder are identical to those in your client's config folder (easiest thing to do is just delete the config in the server and copy-paste the config files from your single-player game).

 

In case you're new to the terminology, the client is the Minecraft game (which you used to join the server) and the server is the text-based thing that you launch with the Forge server jar.

When you say another copy. Do you mean a duplicate or something else.  I’m also having this problem. I just got the server to work and we are all trying to find stuff for this.