When it comes to powering up, the DMD software and the CPU software are independent.
So when you power up. First you will see the DMD software revision and the animation that goes with it. Then after that completes you would see the game animations.
If you get ZERO life, then it has zero to do with the CPU or its firmware level. It has all to do with something wrong on the DMD or lack of power to it.
If you get the DMD coming to life and it displays the DMD Firmware (Its the first thing that flashes, could say "Display Version xxx" or simply the game name "TMNT x.xx" revision but then goes blank when its time to display the CPU revision/ animations, then you have a cable disconnected/backwards, or something more sinister.
You did not mention the machine, but Hook, Lethal Weapon to name a couple only have 1 CPU rom. If you count Display, CPU and Sound you may have 5.
Not sure if mismatched cpu/display would leave you dark as I know if you had say, a Hook Eprom in the display, in a Leathal Weapon pin, you would see HOOK show up on initial power up, then during the game some animations would be 'Hook' where they should have been LW.