I have a JBL Playlist player, which has built-in Chromecast support. When clicking on the cast symbol the player is listed and I can select it. However, the cast symbol then is displayed in red with an exclamation mark, and playback does not start.
Casting works to other Chromecast devices, including a regular Chromecast and a Chromecast audio.
Casting to the JBL Playlist also works with other applications, including Chrome and Spotify (via Chromecast protocol).
Play Services never send the connected event, so Symfonium can’t use the device.
That devices is maybe not compatible with the latest version of Play Service and Google cast libraries, not much I can do here Have you tried to reboot that device and check if it"s firmware is up to date ?
To give this some closure: the issue very likely is the outdated Chromecast support of the JBL Playlist. I tried resetting it etc., but makes no difference. It was a great device, but JBL did give it little support and the latest firmware is very old.
There are apps that can cast to it, like dsub or even Spotify (not sure about the current version, but when I wrote the above it could). But probably those are using some older Chromecast libraries for supporting older devices.
Anyway, casting from Symfonium to actual Google Chromecast devices works flawlessly. Not worth spending any extra effort on the JBL Playlist issue. Just consider it incompatible. I connect to it via Bluetooth instead. Not as comfortable, but works for me.
Have you tried to reboot that device and check if it"s firmware is up to date ?