Apple TV not syncing on my computer

Hi friends,
I have got a lot of problems with my old PC, that's why I decided to buy a MacBook. Everything else is working, except the fact, that my Apple TV is not syncing on my new MacBook. I've been troubleshooting for a couple of days now and I feel like giving up.
I always get this “ is not responding. Check that any firewall software running on this computer has been set to allow communication on port 3689." My firewall is already off.
Do you have any solutions? I'm not really sure what else I can do to eliminate this problem.
Thank you.
