Volts server Minecart issues?

[kaicraft123]

I just made a new voltz hamachi server for me and my friends but when I tried to join it said

Forge Mod Loader has found world ID mismatches

ID 343 is mismatched. World: (ModID: Minecraft, type uv, ordinal 2) Game (ModID: Railcraft, type rc.item.cart.furnace, ordinal 2)

ID 342 is mismatched. World: (ModID: Minecraft, type uv, ordinal 1) Game (ModID: Railcraft, type rc.item.cart.chest, ordinal 1)

ID 348 is mismatched. World: (ModID: Minecraft, type uv, ordinal 0) Game (ModID: Railcraft, type rc.item.cart.basic, ordinal 0)

You cannot connect to this server

please help I REALLY want to play with them on this :(