Hi @rksonos,
Since Sonos will only play what is provided and not downgrade any signal, it’s possible that without passthrough enabled, you won't get anything higher than Multichannel 5.1.
The options I suggest above still exist in the TV settings and, from Sony’s support page for Bravia models, they mention that the location for these settings can change depending on the Bravia model. Passthrough, for example, should be one of the following:
- Quick Settings → Settings → Display & Sound → Audio output → Pass through mode
- Quick Settings → Settings → Display & Sound → Audio output → Audio system settings → Digital audio output → Prioritize pass through
If you still can’t find the setting by following the steps above, or by following your TV manual/guide, I’d recommend reaching out to Sony’s support for assistance in finding and enabling both passthrough and Dolby Atmos on your Bravia 9.