I figured it out on my own after hours of trial and error. For anyone else who's having problems making a modpack for technic for minecraft version 1.13, 1.14, 1.15+ everyone online says "use universal forge file and rename it modpack.jar" but NO ONE says that if you're making a modpack for a newer version of minecraft it will NOT WORK unless you use Forge Installer .jar file and rename it 'modpack.jar'
SO IN ESSENCE USE FORGE INSTALLER .jar file for modpacks on minecraft 1.13+ and for any older versions use the universal .jar forge file