I've got this server with mods. 1.12.2 Modset name is Lapitos Galacticraft. I was playing with friends for two days and finally, I noticed that playing without Applied Energistics 2 is not possible for me. I tried to just add the mod to the modpack and it worked! Once. On singleplayer. Then when I tried to join on my server I saw that error. If I tried to join on a singleplayer it says that "galacticraftcore" is not compatible. What is the reason? Can I even add this mod?

[21:16:22] [Netty Epoll Server IO #2/INFO] [FML]: Client protocol version 2

[21:16:22] [Netty Epoll Server IO #2/INFO] [FML]: Client attempting to join with 135 mods : [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],superfactorymanager@@Version@,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],appliedenergistics2@rv6-stable-7,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]+dev.146.2180b27,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],micdoodlecore@,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]

[21:16:22] [Netty Epoll Server IO #2/INFO] [journeymap]: CLIENT

[21:16:22] [Netty Epoll Server IO #2/INFO] [CodeChickenLib-ConfigSync]: Skipping config sync, No mods have registered a syncable config.

[21:16:22] [Server thread/INFO] [minecraft/NetHandlerPlayServer]: Jagusiatko lost connection: Disconnected

[21:16:22] [Server thread/INFO] [minecraft/DedicatedServer]: Jagusiatko left the game

What can I do about it?

If galacticraftcore claims they are incompatible, that is something you have to ask them.