Thanks for reaching out to the Chromecast Community forum! Let's sort this out.
Quick questions: what type of Chromecast device do you have? When did the issue start? Please reboot your Chromecast device and plug it in on a different HDMI port on your TV. Also, if you have a Chromecast with Google TV (4K), you may try to set up the buttons on the Chromecast Voice Remote. See the steps here.