The reason this happens is because you didn't turn on the TGP while on ground. However, you can correct this in mid-air. Once TGP has been powered on and gone through it's startup cycle (no longer says "NOT TIMED OUT"), If the screen is black with all the options but no video, simply hit the standby button on the MFD while on TGP mode. then hit the A/G button in the TGP MFD page. It should now show video.
