Screen doesnt work until unplug

Greetings to all phone techs and gurus ^_^

I’m facing an issue with my old phone. Specifically, I replaced its screen, but it’s not working as it should. When booting the phone, the logo appears for a fraction of a second and then disappears.

The phone boots normally into the OS, as I can hear the boot sound through the speaker, but the screen remains off. After conducting various tests, I discovered that if I disconnect the screen's flex cable and reconnect it to the motherboard’s main flex, the screen lights up and stays on without any issues with color or touch functionality. However, if I reboot the device, the problem reoccurs.

The screen is not original; it was purchased from a well-known international site.
What would you advise me to do?

Thank you in advance.