PinkieTrash

I've been trying to find an answer, looking at different posts relating to my problem but no answers have been working for me. I don't have much on my computer so it's not RAM, and I can log into singleplayer worlds, but when I try to connect to my friend's server it says "a fatal error has occured, this connection is terminated", no mods were removed and the last thing I remember happening before I disconnected was i got off my horse and my game froze, then I disconnected. My friend can connect fine and his computer is very slow, so I'm not sure if this is something on my end or how to get out of it. I'm not really good with computers, like at all, so I might just be acting stupid. Just to sum it up, I can't connect to the multiplayer server, but my friend can connect to it and I can connect to singleplayer, the game doesn't crash. These are the mods I'm using: Animal Bikes Backpacks (but it for some reason doesn't work) BiomesOPlenty Custom Mob Spawner Custom NPC Mo Creatures iChun Utli Ironchests Kingdom Keys Recoded LLibrary Mantle Morphinh Natura ProectE Realm of the Dragons Roguelike Dungeons torohealth Xaero's minimap My friend checked console and he says it has something to do with Custom NPCs and that's all we can get. Can anyone help?