Black screen after battery and back panel replacement

I replaced my battery last night and put the back panel back on using a book to help press down the adhesive. After which I left it charging and went to bed. When I woke up to check if the battery was working, the screen was completely blank. I did a soft reset to check for signs of life and thankfully there were but still no light on my screen. I managed to unlock my device using the Samsung find my mobile service and open Dex on a monitor so I can at least access my data but as soon as I turn off Dex, it doesn't cast One UI to the monitor. I've also reconnected and disconnected all of the cables to make sure none were loose or damaged (but I could have missed something).