Last I tried, which was a few weeks ago, I was able to use either BubbleUPnP on Android or JRiver Media Center (sometimes controlled by JRemote2) to play on Chromecast. Yesterday, I noticed that the DLNA renderer was no longer detected. And in fact, BubbleUPnP server (on the same Windows PC as JRiver MC) for some reason no longer had the checkbox checked for a DLNA renderer for that device. Check the box, and the renderer is detected.
However, neither the BubbleUPnP app on Android or JRiver can play a track using DLNA anymore. Both act like they are trying to play, but they give up after 5-7 seconds, possibly with 1-2 retries (display jumps back to 0:00), or attempting further tracks on the playlist.
This would be consistent with Chromecast audio unable to connect, as the documentation says. But I can reach the web interface on ports 58050 & 58051 from another PC because the firewall rule is enabled, and cannot if the rule is disabled. I see no other blocks/filters on the Chromecast audio compared to that other PC, all on the same network. This seems like a DLNA problem between the Chromecast and BubbleUPnP server.
Chromecast is able to stream from the JRiver media server, *cast* from JRemote2 (which crashes JRemote2 but does play...).
JRiver (directly or through JRemote2) cannot control the DLNA renderer for the Chromecast. Beeps but no playback.
JRiver is able to control the DLNA renderer on BubbleUPnP Android to play on the phone.
BubbleUPnP app can play to the "Chromecast audio" device but not "Chromecast audio (DLNA)".
Similarly, I can cast from an app such as Podcast Addict. So the Chromecast is working at that level.
Could any of this be happening because the internet is through the first router, and the LAN for all the above devices is behind a 2nd router? Everything has worked fine (to a point) previously under the same setup. No router settings have changed on either router.
Worth mentioning, BubbleUPnP Server detects a different Chromecast w/ Google TV device, nothing is able to cast to it successfully anymore. TV apps on the CC such as HBO Max and Amazon Prime Video have broken, reporting connection issues. Many apps continue to work fine. Connectivity seems normal and fast. All the above have worked recently with the same setup.
I may test these devices on the 1st router's LAN, if something is going on that needs to pass through the routers in a way I do not understand, or a recent update on the Chromecast devices or BubbleUPnP has changed something.