Many people contacted the Twitch Support, they will (99,9999%) fix it, we just have to be patient!
I have contacted Minecraft Support and Twitch Support, Minecraft one answered me that I should contact Twitch support because they can’t do anything.
I’m awaiting for Twitch’s answer.
@Eddie Federmeyer I got the answer from Twitch saying that they are currently working on. On the next days, we will be able to claim the cape!