Deregistered my phone no, can't sign into iMessages on macbook anymore

Hi there and thanks for taking the time to read this.

So, I got sick of iOS and decided to try out an Android phone. After a few days dealing with getting messages on my old phone and not on my new device, I decided to deregister my phone number from iMessages. It worked well, or so I thought. I signed back in on my iPad so I could still get messages from there, but I'm unable to do so on my Macbook Pro.

Whenever I try to sign in on my Apple ID I get the following error: "Could not sign into iMessage. The server encountered an error processing registration."

I've been trying to find solutions online, but so far none have been successful in helping me resolve this issue.

I have an early 2011 Macbook Pro 15", OSX Version 10.8.4

I didn't know exactly where to post this, so apologies if this is the wrong sub-community.

Thanks for your help.