Did you check power cord and cable connection when both video and audio do not work?
1. TV video and audio do not work on TV.
1. Make sure power cord and cables are firmly connected.
How to fix
1. If TV cannot be turned on, check if power cord on the back of the product is plugged.
Check AC power cable on the back of the TV, and also power cord inserted to an outlet.
2. When an multi-outlet strip is used, check if other products connected to the strip can be turned on.
< At the back of TV > < Wall outlet > <Multi-outlet>
3. If letters appear on the screen when you turn on / off the TV or change the channels, press External Input on remote control.