Monitor with Logic Board issue or LCD Panel issue?

I've been trying to fix my Benq XL2720Z monitor for months since the screen got cracked at the corner.

First I bought a replacement LCD panel which was a "tested refurbished unit" but the monitor would power up with illuminated black Blank screen.

Usually for BenQ monitors, there would be a purple splash screen with logo whenever you switched it on, even when not connected to a video source, and you can press menu to access the GUI. But after the replacement I could only see black screen with backlight before the monitor returns to amber light power saving mode. I also could not see any menu options even thought there was the button lights and sound when selecting.

With the monitor connected to the PC, it could detect the Monitor model and info.

Bear in mind, when the LCD was cracked at the corner, the monitor could still display half of the screen. Before buying a replacement logic board, i fixed the monitor back with the cracked LCD panel but the issue is still the same!

I went on to buy a replacement Logic board for this model which is 4H.23A01.A10. After replacing this board, the issue still remains! When I take a closer look at both my power board and both the current and "replacement" logic board, I could not see any visible marks of component failure.

Still I went ahead to fix the Power board, replaced all the small capacitors, the issue still remained. Monitor can power up, detected in PC, menu sounds and lcd monitor backlight all visible but no image or menu splash screen.

Still thinking it might be power failure, i went ahead to buy a replacement power board from a trusted parts supplier. Still the same issue.

I even bought an mstar ISP tool and successfully updated the AUO panel with the correct benq firmware but the issue remains.

I'm running out of patience and have already spent so much in trying to fix this.

Sp far i have replaced these:

- LCD replacement

- Logic Board Replacement

- Power board replacement

- Firmware update on the logicboard with mstar ISP utility board

All of the hardware components look like it has no issues, can anyone help me what might be the issue? Is it the LCD panel which might be botched? Was it the Logic Board that is still faulty? or is it the Cables that need replacement?