Failed to connect to qBittorrent...ConnectFailure (No route to host)

[WC1]

Sonarr version: 3.0.10.1567
Mono version: 6.12.0.182
OS: Linux
qBittorrent: v4.5.2
Debug logs:
sonarr.txt
sonarr.debug.txt

Description of issue:
[v3.0.10.1567] NzbDrone.Core.Download.Clients.DownloadClientException: Failed to connect to qBittorrent, check your settings. —> System.Net.WebException: Error: ConnectFailure (No route to host): ‘http://192.168.1.37:8085/api/v2/app/webapiVersion’ —> System.Net.WebException: Error: ConnectFailure (No route to host) —> System.Net.Sockets.SocketException: No route to host

This used to work. I suspect there was an upgrade/change to either qBittorrent or Sonarr. Maybe something to do with TLS changes?

[MAGAtKiller]

I ran into this and I never looked at the logs, I just change the webui port from 8080 to 8100 and it’s been fine since.

[ClarkHill]

Check your network settings: Make sure you have access to the Internet and that qBittorrent is not blocked by your firewall or antivirus software. Try temporarily disabling them and trying to connect to qBittorrent again.
Check your proxy settings: If you are using a proxy server to connect to the internet, make sure that the proxy settings in qBittorrent are correct. Check your proxy address, port and credentials, if required.
Check the port settings: Make sure that the port specified in qBittorrent is not blocked by your ISP or router. You can try changing the port in qBittorrent’s settings to another available port.
Update qBittorrent: Check that you have the latest version of qBittorrent installed. Sometimes connection problems may be due to an outdated version of the software.
Restart your router and computer: Sometimes network problems can be caused by temporary glitches. Try restarting your router and computer and then try connecting to qBittorrent again.

[WC1]

Thanks for everyone’s replies. Here’s the solution that worked for me…

I first begin the troubleshooting to see if the Sonarr docker can communicate to the qBittorrent docker via ping. The ping failed, so that led me to a network issue. There is something about whether docker containers can see each other, which I had previously configured to allow. For whatever reason, they stopped being able to see each other. The solution was to change the docker network type, and then change it back to what it was.