tldr; Replaced screen, laptop won’t post/boot.  Can still boot with old screen and can hot swap new screen in while running and it works fine, but post/boot checks won't let my laptop start with new screen. Any help would be greatly appreciated.

My Blade Advanced 2020 had an issue with horizontal lines on the bottom of the screen and mirroring the top of the screen.  External displays worked fine.  I decided to try and replace both the screen and the display ribbon cable.

The cable was almost impossible to find, but I found one OEM from another working RZ09-0330, same exact model, I checked all the identifiers on the cable, and everything matches exactly.  The screen was much easier to find, and I got a brand-new replacement model # B156HAN12.0 which matches exactly the model # that came in my laptop.

I removed the charger and battery and did the replacement.  Powered on the laptop, the backlight of the new screen lit up, but nothing.  No post, no ability to get into BIOS, no beeps, no boot, no Windows.  I reconnected the old screen and powered on and everything was fine, booted up and logged into Windows no problem.

Next, I tried some different combinations to see if I could boot without the original screen:

1. Tried new screen + external display plugged in via HDMI. Result: Nothing
2. Tried no integrated screen connected at all with external display plugged in via HDMI. Result: Nothing
3. Tried putting the old display cable back in + new screen. Result: Nothing
4. Tried new screen + pressing function keys to get into boot or BIOS menus Result: Nothing
5. Tried new screen + long pressing (15 seconds) power button before and during reboot as this is mentioned in a Razer support article to test the display. Result: Laptop started, still blank screen, and then immediately shuts down after 6 seconds.  It sounded from the support article this was maybe a way to bypass the post check for the display?  But it just shuts down.
6. Tried new screen + external + pressing F4, this was also mentioned in a support article that it might switch to the external at boot. Result: Nothing

I did some reading, and my best guess is that there is a hardware check at post to see if there is a screen connected to the motherboard, and if it does not see a screen, it will not boot.  This is the only thing so far that makes sense to me that could be causing this, although I don’t know why the exact same model screen would fail to be recognized at boot unless the new screen is bad.

So here is the kicker, this is an older laptop at this point, and while this is not the safest thing to do, I decided to try and hot swap the screens while powered on in Windows to see if the new screen really is bad.  I booted up, logged into Windows, I set my display settings to switch over to my external monitor and use it as primary, then I proceeded to swap the old screen with the new screen and voila!  The new screen works flawlessly.  No horizontal lines, no issues at all, I think the colors might actually even look better.  So, it seems like the new screen in general works.  But now I have a suspicion that it won’t get recognized at boot still, so I restart and, yep, fails to post again until I plug the old screen back in.  I did this whole process again and ran on the new screen for 24 hours with no issues, including some extended gaming.  It kind of seems like the screen is fine but the laptop doesn’t want to acknowledge it at boot.

So, my question now is if anyone else has successfully replaced their screen on a RZ09-0330 or similar model and if you faced any issue like this?  Also, if maybe I am missing something simple, like if there is something in the BIOS I can set (I already checked but didn’t see anything useful).  Could it be possible Razer has custom post checks which ignore 3rd party screens even if it is the exact same model?  Or maybe the screen is working okay, but has some other defect that causes it not to be seen at boot?  My drivers are up to date, my BIOS is up to date.  Scratching my head here.

If anyone has any advice it would be greatly appreciated!  I am also in contact with the company that sold me the screen, they said they haven’t seen this issue before, and they are willing to send me a replacement which I will probably take them up on and try but I have a feeling it is something else.