Hi i wanted play with my friend , but when he wanted join in was error idk how to fix it in log it writed there is problem with library but dont know (Sorry for my english i am Czech)
latest (1).log
1.12.2 forge latest

Download LLibrary 1.7.20 from https://www.curseforge.com/minecraft/mc-mods/llibrary/files/3116493 and replace the old version in your pack.