Why doesn't Twitch recognize that I have Minecraft installed?

I installed Twitch today to play with the Twitch mod packs, but when I clicked the "Mods" button in the Twitch launcher, the Minecraft field was slightly transparent and was not installed underneath. When I clicked on the Minecraft field there was Install but whenever I pressed Install, Twitch immediately canceled the installation.

You first have to go to games in the twich launcher and then on minecraft and install it there (free).

Here is another video from Sparkofphonix