It may either be too far away from your router or it may need an update that cannot be completed over your WIFI. I am assuming you are trying to set the Amp up wirelessly, so I would suggest you try hardwiring it to your router to set it up. Do a factory reset while it is connected to your router. Afterwards you can unplug it and use it wirelessly. 

Thank you for the info.

My sonos is always all hard wired to network and now I have done the reset the same issue is still happening.

Not sure on what else to try.

I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

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 Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Thank you to all for the info.

I persisted with trying to connect and after about 15 goes the amp has now connected.

Thanks again to you all