Shorty

Hey, I've been trying to play on the 1.7.10 modpack but almost every time I try to play it kicks me out. It takes me to the title screen and I click to play and it once it loads up it takes me back to the launcher. It happened all of a sudden, I used to be able to play fine and then out of the blue this happened. I don't know what to do. I've reinstalled the launcher, the modpack, the mods. I did add extra mods but even before I would play with those perfectly. Im using a Mac with Mojave version 10.14.6. Any help would be appreciated. EDIT: I can go into single player mode but not multiplayer.