Have you checked with Integra? If Sonos is working, that suggests the issue is with the receiver, and not with Sonos . I’d suggest perhaps a firmware update on their side might resolve the issue, but that is merely a guess. 

I have a similar problem with my DRX 4.3. Intermittently the receiver will not be able to find the Connect in the Works With Sonos menu (even though fortunately I am able to at least still play music to it) - the biggest issue I have is that starting music through the Connect no longer wakes the receiver so I have to open the Integra app or go to the receiver to do so. It worked at a point but no longer. I attempted to reach out to Integra and they did not respond. 

I have a pioneer receiver and sonos won’t wake mine up either I have to manually change the source 

I am having the same issue with an Integra DRX 5.3 and I just spoke with Integra support who acknowledge that there is a problem but they have no idea what it is and it’s been going on since Sonos released the new version 2 of their app.  I asked if Integra is sitting around waiting for Sonos to call them or is there an active dialog going on between the two companies but the answer I got was I don’t know.

Sounds like the issue is being worked on but no one will give an estimate as to when it might be resolved if ever.