Some additional info would be useful:
- Laptop or desktop. I'd wager based on you post that it's a laptop -- ACPI on laptops is finnicky -- but it's still best to be clear.
- Basic hardware info. Some devices have issues waking (RL example: my controller needed manually waking until about kernel 5ish).
- Does the monitor turn on, yet show no image? This can be "man-patched" by switching to another tty and then back to the video one (I do this on my laptop since Deb 11 broke something that I'm too lazy to fix ATM). If you start X manually, the tty on which you started (usually 1). If your Display Manager, most likely with Ubuntu, starts for you, then it'll be on 7.
- Be more specific about "not start" (see how the above route is very specific to my issue, yet there could be a number of interpretations of "not start", a' la disconnect from and shutdown X server without it starting back up, or a hardware freeze when a component comes out of low power).
Anyway, those are just some.