The problem: I just downgraded my Dell G7 15 7588 following the steps of this video (https://www.youtube.com/watch?v=7zFAU9DKmVk). The downgrade was a success but then I was unable to start the machine properly.

Detailed problem: When I try to start the machine, it turns the power LED on, and then turns off right after 3 seconds. The screen is all black in all cases. And that's it.

Already tried the following solutions:

- Cleared CMOS by removing CR2032 battery for at least 20 minutes.

- Completely removed power battery and pressed power button for 30 seconds.

- Tried starting the computer by pressing D key + power button ; fn + power button ; delete + power button.

- Tried pressing Esc + Ctrl then waited for BIOS Recovery screen, but no results.

Note: This problem occurred right after BIOS update.