First of all, I am using Twitch. Not sure how to get a proper log for Forge based on DaemonUmbra's forum signature - we tried following the instructions for launching the game through the Mojang launcher, but it launched vanilla Minecraft despite us changing the GameDir folder to the pack's instance. I can try this again later after following the video, but this issue is happening on my girlfriend's computer and I'm trying to help her solve it long-distance, as she struggles more with computers than I do, and getting anything from her is... a challenge. (I love her, but it's a challenge.)
The game crashes in the Twitch-associated Mojang launcher, before the window with the load screen opens. It returns "Unexpected error".
I know that Twitch can fail to install things properly, but we've tried "repair profile" to no avail.
The pack I made for us only contains 8 mods, all of which were obtained through Twitch (No 9minecraft or whatever the site is):
AppleSkin-mc1.15.2-forge-1.0.13.jar
backpacked-1.4.1-1.15.2.jar
FastLeafDecay-v22.jar
Hwyla-forge-1.10.8-B72_1.15.2.jar
journeymap-1.15.2-5.7.0beta1.jar
jei-1.15.2-6.0.0.3.jar
Neat 1.6-20.jar
OreExcavation-1.7.151.jar
The packs I've made for 1.12.2 work fine, and this pack works fine on my computer as well. I made sure to not get a Fabric version of Hwyla on accident, and the mods seemed fine while playing when I tested the pack on my machine.
The error it was giving her in the latest.log file was something about Forge not being able to find Minecraft. I tried sending her files from my install of it, but the game still crashed even with those. If none of this is gives any idea what's going on, I could try and get her to send the latest.log file if that would give any useful info. Any help is appreciated.