

+1 to this.
First check that you can get to Jellyfin on your Jellyfin server itself (start with the IP address). This makes sure that the service is running, and that you are trying to access the right port/protocol.
If that works, try the web browser on your phone or any other device on your network next. If that fails it tells you there are firewall or DNS issues.



I don’t use the WebOS app but generally default subtitles/audio languages are set on your profile and the apps pick up those settings.
Try logging in to the web interface and going to your user profile. There is a “Playback” section where you can set your preferred languages. If this isn’t set it likely is taking the default language from your media files instead.