Did you export it the way the Twitch Launcher does with a manifest file, modlist and a few other things? That's basically the way they want to you go about exporting your pack. I did what you do with configs, mods and otherwise in a zip file in the past the first time I wanted to upload a modpack to them and they rejected it. But since I've learned how to upload modpacks to them and not get rejected, just sometimes with my descriptions being a bit lacking sometimes, but otherwise I've been fine since. If you use the Twitch Launcher, create the modpack, select the mods and do your part with the resources then I assume when you export it will be fine.
If you want to be quick about it to understand the approach they request. I'd recommend just creating a quick pack, with a few mods and launch the game to get the configs at least, quitting the game and exporting it to understand what they are after so you allow mods and configs. Mods will be a modlist file which it will check with those listed and download them basically, not having them in the folder already which kind of sucks, and configs all are there though which makes the mods not being there but requiring a download really annoying but it's the way it is. But yeah, if it isn't exported that way with the necessary files like I said they will reject it, since they basically want you to give an automated installation of the modpack to the Twitch Launcher rather than just a setup like you have. Once you understand what they want for the mods/configs you can probably work the resources into it from there I guess with the same mods, same configs you had before. 'Hopefully'.
Take a look at my modpacks for descriptions if you want as well as look through the requires of the 'prior to upload' process of a modpack again to be sure your getting it right. I had considered making a video on this but people probably have already and not much might have changed.
Niche Mod Finder/Acknowledger/Tester/Player. Fan of Datapacks, Rift 1.13/1.13.2 Mods, Fabric 1.14 Mods and interesting underrated or new 1.12.2 and below versions of mods. :) Testing 1.13.2 Forge and Fabric 1.14 mods mostly though.
I sometimes create the odd modpack or adventure map once an idea comes together.