The configuration to use is ‘grouped’ rooms. See this link:
https://support.sonos.com/en-us/article/group-and-ungroup-rooms
Its okay for music audio output, but not ideal for TV audio, that’s if using the speakers in close-proximity in the same physical room, as there is an audio-buffer delay between the speakers of 75ms or greater.
To resolve that audio buffer delay you could ‘bond’ rather than ‘group’ the speakers as surrounds, but to do that you will need a second Era-300.
I am able to add my Era-300’s as an ‘accessory’ to Apple HomeKit - if you’re having difficulty doing that, then perhaps try rebooting the local router and/or bringing the speaker nearer to the router. Also reboot your iOS device and try adding it to HomeKit again. If the issue still persists with HomeKit, then it maybe best to submit a Sonos system diagnostic report from within the Sonos App and either note/post it’s reference back here and then contact/chat with Sonos Support Staff via this LINK and see what the Staff can suggest to resolve the matter.
I still have them grouped, but when In listening to tv, both speakers keep changing sound.
most of the time, both of them are working, but some other times, era 300 “turns off” and beam is only working.
why is that happening?
thanks