Modpacks load than don't launch

[marshwalker2]

I am an admin on a MC server that recently made a Tekkit Classic server. I will open up the launcher and open the modpack. The modpack opens as if it is working, then it just brings me back to the modpack launch page after loading. Please tell me or link a video on how to fix this issue. I have tried re-downloading the modpack and launcher. I have also tried playing with various settings like ram and folder options.