Minecraft on Twitch is not working anymore?

I installed FTB 3 via Twitch, it has been working for months. If I want to start this again, I get an error message that the system can't find the specified file. I also updated everything and also tried to rebuild the profile, but it still does not work. And in the folder, all files should still be present, because I have not uninstalled anything.

Just try reinstalling the pack. Simply as a new profile. If it works, you can simply copy your map and settings.