Mr Random

When i try to start modded minecraft it either doesnt start but makes the launcher think it does or start ignoring the modpack in my mods folder this is my first time with modded minecraft so its probably a simple mistake

For some reason when i try to play modded Minecraft it either doesnt start but the launcher thinks it did or it does start ignoring the modpack in my mods folder. ps its1.12.2 pss this is my first time trying modded Minecraft so its probobly a really simple mistake.