iMessage not accepting my Apple ID

So one day I find that iMessage isn't working. I'm still using an old iPod Touch running iOS 6.1.6.

So, here is the screen I am greeted to when selecting the messaging app.

Strange, because I've been using iMessage for a while. I haven't synced it in a while.

So I press get started and enter my email and all that jazz.

I press sign in.

And it brings me to this screen.

I press next...

And it brings me back to this, for an endless loop.

Now, this isn't a problem localized to my old iPod. Here's a video of logging in my account vs another one on a mac running the latest software:

Apple error - YouTube

Again, my account doesn't work, but another one does.

I didn't change anything, I didn't even sync my iPod. I already tried restarting my iPod, I've already changed my password. My contacts are still there. Oh and another thing, I can't send a text message to my email from another device. The "not delivered" message appears.