The Sonos app is just a remote control. Submit a diagnostic and reply here with the confirmation number; a technician will get back to you.

I sent one earlier today at the time of latest issue.

After 2 hrs I got it working - but I have just run another diagnostic (1652024082) - although it is working currently.

most weeks I struggle with the App. 

So you sent a diagnostic earlier today. But as you did not publicate the number at that time in this forum or contacted Sonos Support, nobody knows about it.

You even do not explain why the app is “so bad” or “never works”, so none of the forum members has a chance to help you.

Now wait for a Sonos employee to pick up your latest diagnostic number - or call Sonos Support to discuss it.

Hi ClausN,

Quite a rude - unhelpful response. I did not know I needed to publish the diagnostic number on this community.

The app is just blank, unable to find my system or select music.

At the risk of sounding unhelpful, I’ll say “not me”.
 

If it helps you with your setup, I’ll also tell you that I’m running in SonosNet mode, with wifi and SonosNet on channels 1 and 11, and have fixed ip addresses for my Sonos devices. Since setting up this way, several years ago, problems have gone away. 

@AndyK55

I didn’t mean to be rude, but your “it just never works” does not leave any chance for a forum member to assist you.

It is not clear which steps you have taken to solve the issue, but now that you have given a bit more information, I suggest that you refresh your system in this order:

1: Power off all Sonos devices

2: Restart your router

3: Wait for the router to fully restart, then power on Sonos

4: Restart your controller(s) (phone/pc etc)

Ensure Sonos and controllers are updated with latest software, and check for wifi interference:

https://support.sonos.com/s/article/3286?language=en_US