Screen malfunction on Sony Alpha 77

Hello,

My Sony Alpha 77 has been giving me some trouble for the past few days.
The tilting screen remains "black." To clarify, it's not completely black; you can clearly see that it is powered, but it shows nothing, as if the HDMI cable of a DVD player were unplugged from a television.

After some research online, I ended up replacing the screen, but the new one hasn't changed my situation.

That said, it doesn't prevent me from taking photos, especially since I'm not a fan of framing through the screen; however, it's not very practical for viewing photos and even less so for adjusting the camera.

Does anyone have any idea what might be causing the issue?
Is it a software or hardware problem?
Is it repairable, and at what cost?

Thanks to those who will take a few minutes to discuss this with me.

Have a good day.

Christophe