If both the original and the replacement do not function, I would look to take a trouble light and confirm the power lead is good. Although less common, check that the ground is intact. Hopefully you have a known working spare strobe head you can plug in to confirm all the lights were not killed for some reason.
I once had all the lights on a Federal Signal MX7000 die at the same time. I wasted a lot of time tracing wires until I tried a new bulb and found some spike had killed all the bulbs.