It is entirely possible the screen or one of its parts got damaged in the process, but the first thing to do is double-check your work. In particular the OLED connector is the one you want to pay attention to. It's this one.
So yeah, open the phone back up and disconnect the screen. Use a magnifying glass and a bright light to check the connector both on the cable and on the logic board. Look for any dirt, debris, broken or bent pins that might interfere with a good connection. Also examine the flex cable for any tears or extreme bends. Assuming it looks good, clean both sides of the connector with 90% or higher concentration of isopropyl (rubbing) alcohol, let it dry and reconnect it. Pay particular attention to the note on Step 20 of the Battery Replacement guide.
To re-attach press connectors like this one, carefully align and press down on one side until it clicks into place, then repeat on the other side. Do not press down on the middle. If the connector is misaligned, the pins can bend, causing permanent damage.
If nothing helps then it would be time to bite the bullet and replace the screen. I've been finding them cheaper and cheaper; nowadays you can get a soft OLED screen for $35 or less; the last one I bought was only $23 USD! I know it seems suspiciously cheap, but I installed it and it worked great and looked good. The only odd thing about it is that it doesn't come with the plastic camera mount where the earpiece speaker sits, but it's not difficult to pry the old one off the original screen to reuse it.
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