FIX Screen sharing and file transfer not working in Skype [Windows]

Open a command prompt and run the commands:

net stop winnat
netsh int ipv4 add excludedportrange tcp 50000 60
netsh int ipv6 add excludedportrange tcp 50000 60
netsh int ipv4 add excludedportrange udp 50000 60
netsh int ipv6 add excludedportrange udp 50000 60