Mac won't send messages

I just bought a Mac Pro about 2 weeks ago so mine is still new. When I got it, I noticed that I was able send messages to people without iPhones which I thought was pretty cool. Well, two days ago I got a new phone because my family switched providers and I got the iPhone 6, and I'm not able to send messages to people without an iPhone on my Mac anymore. I don't know if there is something I have to do, but I can't figure out why it's not working anymore. I didn't get a new number I kept the same one.