LED Screen won't go on

The power button on my iPad Pro A2301 (2021) became jammed inward. I tried everything, but couldn't get it to pop back out. I couldn't find a repair shop that was willing to even touch it. So, I came to your site and found excellent instructions on how to fix it. I ordered the tools and did it! It was like performing surgery. I'm not experienced at fixing computer devices. I opened the unit without breaking the screen and got the button unstuck. The ipad even turned on. But now as I'm trying to put it back together, the screen won't turn on. When I plug it in to the power supply, it makes a chime. So, it is powering up. But the screen won't go on. How do I trouble shoot this problem? How do I know if a power ribbon was not put back correctly, or maybe I damaged one of them; or maybe I damaged the LED screen beyond repair. I don't know how to diagnose the problem.