Bose Cinemate not producing sound for cable box, but works for Bluray on new Smart TV?

Dec 14, 2018
Hello. I have an older Bose Cinemate 1 (only RCA cable output). I just purchased a new Smart UHD TV that ONLY has optical/HDMI inputs. I bought a digital/analog converter from RCA to Optical, but I only get sound when the input on the TV is selected for the HDMI for the Bluray, and not the HDMI for the Cable box?