Are you reserving IP addresses for the SONOS units? Make sure that the input plugs are fully seated in PORT. If you are having an issue here the Line-In might disappear erratically.

Perhaps see if setting the Ports ‘Audio Delay’ option to 150ms (or higher) resolves the matter for you.

I have never reserved IP addresses for Sonos or anything. Not sure why I would have to do that now. Is it required by Sonos with this latest app update?

I will check the audio delay, but it has always been set at Low/75ms and worked perfectly.

All cables are seated perfectly and working fine.

No it is not required, but Sonos updates require units to reboot, and in a small proportion of cases the router will get confused over reallocation of IP addresses. Reserving IP addresses virtually removes this risk. It's entirely up to you whether or not you make this small improvement to your system. 

Yes, I reserve my Sonos IP addresses - it just gives that added reassurance that duplicate IP addresses are not going to cause a problem. I’m still interested to see if the buffer adjustment to 150ms in the ‘Audio Delay’ setting may work in this instance, as networks are often affected by many changing external factors too.

One can accidentally get away without reservations 100 times in a row. On 101, when a duplicate is created, the incorrect assumption is that “something broke”.

I wish I had kept a count of all the “update broke my Sonos!!!” posts over the years, triggered by IP dupes caused by a forgetful router.

Usless. Why bother

Changing the audio delay to High and Max didn’t change anything. System still cuts out even after rebooting. Will try this IP Address reserve. I still don’t understand why my system was fine for 2+ years and now it isn’t.

Possibly because networks aren’t static, but subject to all sorts of vagaries? Things can change, and most frustratingly to folks like me, without any intervention on my part. 

At this point we don’t have the data to prove that duplicate IP addresses are an issue for you, but reservations is an easy way to reduce the risk of future surprises. By the way simply making the reservations now might not cure an existing duplicate address issue. You’ll need to reboot everything before making the reservations or wait until enough leases are renewed that duplicates fade away.

We cannot rule out hardware failure.

While in trouble shooting mode if one assumes that the issue must be s...] or cannot be o...], one is likely to be blindsided.

Reserving th IP addresses did not work. Issue continues.

I have no idea what the issue is. All I know is everything worked perfect then the app updated and now it doesn’t.

Reserving the IP and upping the Audio Delay are out.

What else can I do?

After doing my daily router restart, now the app is telling me that my phone and Sonos are not on the same network - they are - and it is going through set-up procedures. It’s been “Getting your Sonos Arc ready” for about 5min now.

Submit a diagnostic immediately after one of these events and again after your workaround. Post the confirmation numbers here. SONOS staff can comment. Note that reboot deletes most of the interesting diagnostic data.