Help! Having trouble with iMessage.

Hello all! I just bought a brand new MacBook Air (2015) and I can not get iMessage to sign in. The first thing I did was update to the latest OS. iMessage is working on my iPhone, iPad, and Apple Watch. I am signed into iCloud on my MacBook. I click the messages icon at the bottom, enter my Apple id and password and hit sign in. The sign in button goes grey for about 3 seconds and just turns blue again like nothing happened. I am not receiving any errors or anything, it just isn't letting me sign in. I have also tried to sign in to FaceTime but there is just a loading circle that goes on forever. Can anyone help me? Am I doing something wrong? Thank you in advance!