Have you done the steps in the web interface, yet?
When using other players on this device, like Squeezelite, make sure that these players do not exclusively block or mute the sound card. Add ‘-C 10’ to the Squeezelite commandline settings in advanced options on the Audioplayer tab, to tell Squeezelite to disconnect from the soundcard after 10 seconds if nothing is playing and make sure to remove the ‘-Q’ option. Otherwise, the volume will be set to 0 when Squeezelite is paused.
Make sure to ‘Disable IPv6’ in Raspberry Pi Settings (if not disabled yet).
Also, do you have any command line options set up in the player’s interface?