The Optical input is transmitted via a light beam at a fixed volume level, as a result the signal from the TV to the speaker does not allow volume adjustment.
However, the latest firmware version p14802.190 this has been addressed.
The latest update shall enable the speaker to change the Optical input volume of the PRO Speaker within either the Player or Rooms Page with the Lithe Audio App
Please check to see if the speaker has updated automatically via the app, to view this, navigate to the Speaker Settings page towards the bottom.
If the update has not applied after the PRO speaker being active for more than 6 hours, please contact us and we will be able to help you further.
If you are looking for a wireless solution from your TV to the Pro Speakers, we suggest our WiSA bolt-on and SoundSend transmitter. This would then allow volume control on the TV remote, Plus Dolby Atmos capability when used as part of a 7.1 multi speaker setup click here