i'm not able to send messages on my macbook air (2013) but was able to send messages on my macbook pro (2017)

The title pretty much explains it all.

I rushed to make a new purchase for a brand new and current MacBook Pro before scouring the market for something more affordable and in my price range. So I found a MacBook Air 2013 version for much cheaper and was still able to save a lot of money in the long run. (Broke college student yay!)

Anyways, when I set up my MacBook, I was able to send and receive messages from android users, but for some reason I can't send messages to android users on my MacBook Air. I'm not sure if it's because it's a different processor, but I did give the Air a software update to Mojave.

Please help me!