cant get mag 254 to work on my big tv

sometimes it also helps if you shut tv off and on cause hdmi cables do make differences with some tv and try what vampirito says,I had one hdmi that went bad and changed it and got it working.
 
ive tried every resolution on my big tv mits 73 inch rear proj with hdmi cables cant get it to work
on my smaller tv works fine on 480 with rca cables

Unplug MAG box, hold menu button on remote, plug STB back in still holding menu, enter bios change video setting to auto exit save