If the Playbar was not used for a really long while, it may need to have an update pushed to it.  Contact Sonos support and explain the situation, they can force an update if that is what it needs.

1000-type errors can often be overcome by using the desktop Sonos app for Windows or Mac (Google these to download from the Sonos website). While it is hardwired and recognised, run the system update from the desktop app. 

Thanks
I’m not sure they can push the update until it’s added in my system…
I’m also using the windows app unfortunatly when I look for update it tells me I’m up to date.
Probably as it can’t see the new Playbar being in a found state but still not added to the system.

Is there a way to take your Boost out of the equation? There have been some Boost support issues with the new app, I believe. Plus, as long as you have one speaker connected to the router by Ethernet (if that’s feasible for the location), your speakers will create the same Sonosnet network that the Boost does anyway. I just wondered if the Boost had become the weak link in preventing the new Playbar setup. 

Pushing an update is how they solve the problem where the firmware is so out of date that you can’t even add/update via Ethernet.  So they most certainly can push an update to a unit which isn’t added to a system.

I removed the boost and pluged my working playbar to the network.
I then use the 2nd port to connect the new playbar, but still the same problem.
I guess I’ll have to contact Sonos on monday ...