Check to see if the power cord came unplugged from the cable box, TV, or VCR.
Press the PWR (Power) button on the remote control. If the TV did not come on, go to the front panel of the TV and press power On. If the TV came on, then the batteries in the remote may be depleted and should be replaced.
Press the CBL (Cable) button once on the remote control.
Check to see if Parental Controls were set to block the channels. (To unblock programs, press Settings on the remote control and follow the prompts. For additional information, see Parental Controls in the Technical Support area of this website.)