All Vizio TVs utilise backlight lamps which determine how lit up the screen of your TV is. The backlight is an entirely different setting than the brightness and contrast settings, which directly control the black and white levels of the screen. If the backlight setting on your Vizio TV was turned off, the picture will be very low-lit, which makes for a picture that is difficult to see. Turning the backlight back on will fix this problem.
Turn on your Vizio TV and press the "Menu" button on the remote control.
Select the "TV Settings" option and then choose "Picture."
Choose the "Backlight" setting and then use the right arrow button on the remote to turn the backlight back on and adjust it to a higher setting. When you are satisfied with the backlight level, press the "Exit" button on the remote to close the menu.