Hi, I've been searching alot on how to fix the problem and I've come to a solution. I've had the same problem trying to connect to my friends server. Well some of my friends were able to join and some werent. Now realize how we are from the same country. In our country some people prefer to use their computers in English and some use it in Turkish. This is a setting you set when you first get your computer. I dont think it can be changed again unless you re-install Windows. So I dont have an explanasion for this but, when forge downloads the config files, if the computer is set to Turkish, for some reason it adds in another item. For example in your situation:
There should normally be only one of the item named " item.artifice.sledge.iron".But when it is a Turkish version it also adds an item named "item.artifice.sledge.ıron".If you realized the "i" letter is diffrent in these two.
In my situation my friend uses a Turkish PC and opens the server. The server creates these two items. But when it comes to my PC it only creates the item named " item.artifice.sledge.iron".
Since there isn't the letter " ı " in English.
So when I try to enter the server it searches for these two items. It finds " item.artifice.sledge.iron " But it cant find the item named "item.artifice.sledge.ıron " on my client.
Heres the solution. The English PC user must send his config files to the Turkish PC users. *
*IMPORTANT
It Wouldnt Work The Other Way Around Since When you send the Turkish config file, it includes the item named "item.artifice.sledge.ıron". Since this item includes the letter " ı " English PC's wont be able to understand this letter and it would put other random letters instead of it, which would cause another bunch of problems !
The Config Files Are Located In : "Appdata\Roaming\.technic\[Whatever Modpack You Are Using]\Config"
I hope this helps you. Good luck on fixing the problem!
