You may have to configure Windows Defender to allow AirServer & mDNS. In order to achieve this, you should make a firewall exception for AirServer within your Windows Security firewall settings. 

Windows Defender (Windows 10)

1. Open up Settings from the Start Menu.
2. Go to "Update & Security" and open "Windows Security".
3. Press "Firewall & Network Protection".
4. Click on "Allow an app through firewall".
5. Press "Change settings". 
6. Scroll down to AirServer Windows 10 Desktop Edition and make sure it is allowed on both Private and Public networks by ticking the boxes.
7. Scroll down to mDNS and make sure it is allowed on both Private and Public networks by ticking the boxes.
8. Press OK and reboot the computer.