I am on a mac (I've seen others with the same problem that were also on macs) and i definitely linked my twitch.tv account in the snapshot but when i press F6 a message appears saying "You cannot broadcast to Twitch whilst you are playing offline. Please go online and restart Minecraft". PLEASE FIX SOON!
MC-40814
Mac "Cannot Stream"
Resolved
Duplicate
0
Note that if you need to be using version 10.8 or higher to support broadcasting.