Black screen after lcd+sceen replacement

Hey ! I just finished replacing the broken screen on my op5 and now it won’t turn on. I can feel the vibrator and see the red LED when powering it up but the screen won’t display anything.

I read here that it can come from the version of Android installed on the phone, but I don’t have a screen to perform the downgrade.

Any idea about what could have caused it/how to fix it ?