1 Reason

It's usually because incorrect monitoring adapter settings or the monitoring adapter is not supported.

Please notice that most wireless network cards are not supported.

2 Solution

Check "System Settings"->"Monitoring Settings", to ensure the monitoring devices are properly configured.
Ensure you're using a wired network card as the monitoring device.
If you're not sure about the "IP Segments" settings, leave it as blank.
If no adapter appears in the monitoring devices, please reinstall WFilter and reboot your windows to check.