Do you have the ports open as required?
You have a static IP address? On the Mac go here: http://whatismyipaddress.com
What is the IP Address listed?
OK and you tried that IP ?
I port scanned it nothing
I scanned it from here there are no open ports. If you go here on the Mac does it open the server?
Make sure you have System Preferences / Network set to Manual settings with that IP address etc... also restart the Airport router
Yes did you restart the Airport router?
If you open your Network Utility (/System/Library/CoreServices/Applications/Network Utility.app) and try pinging that IP address it gets 100% packet loss so that IP address is not accessible.
I would reset your Airport router to factory settings then set it up again.
Ok I have mine connected directly not by WiFi and I think that will get you better results too
Make sure it is a Factory Reset: https://support.apple.com/en-us/HT201945
I assume it changes what is it now? Also who is you internet provider?