I tried installing, reinstalling, reinstalling pack and reinstalling the client. All I get are closed errors. Also, when I uninstall the client from packs, I am unable to load the pack again. I am forced to download a pack again.
I am using the 1.12.2 version on MultiMC. I have tried using the .jar installer, but not the manual install as that seems to only install a version for the vanilla launcher.