Minecraft via Twitch app?

I got the twitch app again today and wanted to play Minecraft with mods again. But when I go to Mods and then MC always comes up with "We seem to be missing something. Click on the button below to get started." And even if I press extended and want to change the location is nothing. I press the button and it will not "load" for a second. Minecraft is also grayed out there and not installed. The normal game I have, in the latest version, 1.12 and 1.7.10. I can also play normally or go to server. Only with Twitch works there nothing. Do I need to delete an old file path because I've had it before and it can't be overwritten or something? I also searched for the file under which it should be saved but there was nothing found.

Are you logged in? Of course you have to buy the game, maybe the account is not registered or something