Lionchief Plus 2.0 no longer has a physical volume pot for manual adjustment. It is all done digitally either via the Bluetooth app or TMCC control.
The manual https://www.lionelsupport.com/...20Genesis%205.22.pdf
Also, there is no signalsound VS Railsounds switch as in the past
So, when connecting via bluetooth, you also ensured you raised ALL volume controls to max right?
You click on the speaker icon from the home page when connected
If it still doesn't work, then probably needs to go back to Lionel.