The firewalls on both computers are not allowing to receive notes. Kindly configure the PC firewall to allow Notezilla . Do this on both sending and receiving computers.
You can search for firewall in Windows search box and you will see Allow an app through Windows Firewall . Choose this option and enable Notezilla . If Notezilla is not listed, then click on 'Allow another app' and add Notezilla .
If you are using any other Firewall tool (usually included with Anti-Virus software) then you will have to configure that firewall.
Make sure you do this on both the sending and receiving computer.