Help with Magnavox my surround sound

[Bill1994]

I have and older Magnavox tv and a Sony Am FM surround sound and a Sony DVD player all hooked to the tv with RCA cables, everything worked fine for years ( no cable ) , just streamed everything from Roku and and through the DVD player. Last week my wife wanted to get cable turned on. The cable company came and installed two boxes for the cable and now my surround sound DVD player and Roku will not work " communicate " if you will " with my tv. So my question is what setting up the cable setting do to the setting in my tv. The cable company was no help at all they said buy a new tv