One or more of your HDMI inputs should be labeled as a CEC (or possibly Anynet+) input.
If you are connected to the CEC input and it's not switching, it may have been disabled. There should be an option in the tv configuration to enable/disable CEC. If you can't find it, try searching google for your TV model and enable CEC...
Hope this helps.
Current RV Information: 2018 Forrest River Salem Hemisphere 282RK
Previous RVs: 2004 Fleetwood Bounder 32W; 1999 Four Winds Five Thousand 21RB; 1986 Allegro Bay 27'