I have downloaded Minecraft 1.9, but when I click "play", the button either does not do anything of switches to saying "loading" and then revert back to saying "play", and will not load the game. This is using the minecraft launcher 1.6.19 ( the minecraft.exe version). I have used the other minecraft launcher (minecraft.msi) before but had to switch because it stopped working.

How can I fix this problem so that I can launch minecraft 1.9?