I took this title from a thread that was locked about 4 weeks ago by @Phlynn. I'm having the exact same issue with my STR-DN1080 receiver.
My issues started back in December. I noticed that the receiver wouldn't stay connected or would pause on its own. Cone January. Now it's not being recognized by the speaker groups but I'm still able to stream music via voice assistant. As February went on, all of that deteriorated to where it's not being seen by the speaker groups, not being seen by the voice assistant, and now I'm not able to manually cast to the receiver. Connection is intermittent.
I saw no solution in the locked thread. Like I said, the issue started in December for me. I've been calling Google home and they could only direct me to the manufacturer. I called Sony and they were stumped at the fact that I knew more about the issue than they did.
After 2 months of back and forth, it's now known to Sony (at least what I'm being told on my ticket) and it's being escalated to their engineering dept to see if they're going to push a new update. The issue is with the Sony device having an outdated Chromecast firmware version. From what I understand, Google is now pushing firmware version 1.57. Sony is still on version 1.36.
Now the truck becomes, how do we get Sony to reconcile this issue. There's really nothing Google can do aside from having someone from the Chromecast software engineering depth get with Sony to give them a boot in the tush to get moving in this resolution.
I received a call from Sony's Software engineering department. They hinted around my receiver being out of warranty and they may not be sending any more updates to my device. He said that I would need to go to google to get the update to the firmware. I told him that google cannot send an update to their software and there is no need for a full blown update. All they need to do is send a patch containing the updated Chromecast firmware version. I told him this is not an isolated case. He said there are several more tickets with the same issue. He said he will send the patch suggestion back to the engineers and get back to me in 48 hours. I'll send another update then.
Thanks for reaching out to our Community forum.
I want to check if you already got an update from Sony's end and whether or not they will send a patch for the built-in Chromecast of your Sony STR-DN1080. In that way, we'll be able to determine our next step since we need this firmware update for it to work seamlessly with the Google Home devices.
Keep me posted.