Custom modpack won't open

[TimeyWimeyWIllow]

Hello,

I've been trying to make a custom modpack for my friends and I to play on, not a very big one, maybe 2-5 mods max. I got everything set up fine, but the problem is when I go to try and run the modpack I will click play, the loading bar will fill up, the launcher will disappear like the game is about to pop up, and then the launcher just pops back up again. This is my first time making a pack so I feel like I definitely missed something but I'm not entirely sure what I did wrong or what errors I'm looking for. Any help is appreciated, thanks!

[JaariAtmc]

This belongs in Platform Pagoda.

Any inkling on what the name of your modpack is?