Probably not getting sent a high enough volume signal from the TV.

Tell us more about your setup and maybe get a more detailed suggestion.

Or, it could be that the optical cable isn’t inserted in one end or the other, or both properly. Or that the cable has the little caps that often ship with them.

What is “low volume” to you? Doe the Ray not go loud enough or is it just that it needs a higher volume number/notation on the TV?

Pretty much even cracked up to max, it's still seems lower than what i typically had before with just TV alone.

Very simple setup with Samsung 4k UHD Curve 65" (model UN65KS850DF), streaming on FireTV 4k and then beforr xmas added brand new Ray Soundbar with 2x Era 100, and Sub-mini.  Below is the info on what I have and how it's setup - but trust me, I am pretty sure have read  prob every instruction, definition, guide, article, blog, and post on Sonos website as well as here on the communitysite.  I literally went through most of not all questions, and attempted every setup, every setting change/update, and possibly every troubleshooting tip I found online. 

Every SONOS setup was completed with the exact steps as requested in the guided wizards.

Optical cable seems fine, caps are off, plugged in correctly and connections look good,  per instructions.

TV - I tried so many different variations of sound/audio settings - including suggestions by you guys here in previous posts

The only one thing I haven't tried is delete everything, factory reset and start from scratch