Hi @Pjt96j 

Welcome to the Sonos Community! And, apologies for the delay.

I’m sorry to hear of the issue you’re having with getting your Sonos system running on a different WiFi!

I do see that your system is currently online, however - are you still having this issue? I assume not, but please let me know if you are making do with an ethernet connection you’d rather not use - I’ll be happy to assist.

Looking at your system now, I can see that one of your Sonos products is on an older version of the speaker software than others - this can create issues with grouping, and in your case, possibly Home Theatre performance too.

Please open the Sonos app and check for updates: Settings icon » Manage » System Updates » Check for updates to resolve this. Thank you.

I hope this helps.