If the message still appears on the TV, contact the provider of the set-top-box for further support.
Note: To verify that the TV is not the issue, connect any other device via HDMI (such as a blu-ray player) to see if the error appears again. If it does not appear with the other device, then the STB (cable box) is the issue. Connecting the STB with a set of component cables will resolve the issue temporarily until the cable provider can resolve the issue with the set-top-box.