The most common reasons of network communication error are:
1. AVChat is not enabled in the firewall of Windows, or/and in the firewall of the virus protection software (if exists), or/and in the firewall of the router (if exists).
Solution: Check the settings of all firewalls.
2. UDP protocol is not enabled in the router (if exists).
Solution: Check your router's settings, if it can block UDP communication.
3. Connecting through proxy server, and proxy server is not configured to enable UDP communication.
Solution: Change your proxy settings.
4. Running torrent client in the background consumes too much bandwidth.
Solution: Stop torrent client to see if it helps.