I’m going to guess that you have a PLAY:1, not a Sonos One, but the software connection to your computer is the same for either speaker.

What’s not clear from your post is how the Sonos speaker is connected to your LAN. Is it hard wired to your router with an Ethernet cable, or does it just connect to your WiFi signal?

The symptoms you’re describing could be as simple as wifi interference , or possibly something more challenging. Beyond the information in that FAQ, I’d also recommend a simple refresh of your network, by unplugging all Sonos devices from power, and while they are off, rebooting your router. Once the router comes back up, you can plug back in the Sonos devices.

But, if neither of those resolve your issue, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this ’library not found’ error, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

Try unplugging the Play:1 from power for about a minute and reboot your router and desktop computer.

Is your computer set to fall asleep?

Further thoughts…you may want to also check the settings for the hard drive on that computer where the library (iTunes) is stored. If it is set to ‘sleep’ after a period of non-use, that will also cause issues for Sonos. You would need to set it to always be ‘on’.

Is the speaker, or desktop PC, wired to the LAN, or running on WiFi? If running on WiFi what is the WiFi channel and channel-width in use?
 

Also is either the desktop, or the speaker, near any other wireless products, assuming they are not wired?

Has power-management been switched off on the desktop so that it doesn’t go into low-power mode and switch off its network connection or power down its HDD’s etc.

Hi Airgetlam - Thanks for your response. 

If my desktop is connected to the monitors then it is on a wired LAN (Hub).  But ultimately the majority of the time, it’s wireless.  I think you are probably correct in that it could be wifi interference as after I posted this, it started to play again - I also get issues with my work laptop on Teams calls where sometimes I can be heard, other times, I’m dropping in and out, so I end up dialling in with my mobile which solves the issues, but I guess that could be  3G/4G kicking in if the wireless drops etc

I’m not sure how I can resolve the Wifi as I know my mobile signal can be poor - I’m in a ground floor apartment so I think there is lots of steel around me.

I need to think about my set up or maybe get somebody technical in to maximise what I have!  

Hi GuitarSuperstar

Thanks for your response.  The DT is never asleep, so I think it is probably as Airgetlam stated, wifi interference as it started to play again after I posted 

Hi Ken

Thanks for your response.

My wifi channels have been split to the 2 /5ghz.

DT is underneath the SONOS speaker - both are wired (electrical) - DT set to never asleep.

I think it is probably wifi interference, so I need to look at my overall set up and see how I can maximise the wifi signal or have everything on LAN.

Read that FAQ that I linked for more information (the underlined words). You may also be better off wiring one Sonos device (any, if you have more than just the one) to your router, as well as wiring that desktop to your router, both with Ethernet cables, if at all possible. That would alleviate most of any potential WiFi interference, although if you have more than one Sonos speaker, any of the unwired ones would be potentially affected, just not the desktop and the wired one.
 

The diagnostic I suggested would also give Sonos support some hard data to look at, if you’d prefer. I certainly recommend it, doing network diagnosis via text is always potentially troublesome.