Model XT1609 Questions afteer LCD replacement

Hey there! I’ve been using t teardown guide for a few years to replace my cracked screen (3 times in 3 years) I bought the screen and LCD digitizer as one whole part online, and moved the guts of my phone to this part. I realized that I didn’t connect that audio/speaker cable and disassembled my phone to put that part inside. My screen will not power on now after powering on previously. It just vibrates and that’s about all I get.

Why would this happen. Also, would the flex cable that’s behind the battery that connects to the motherboard and the charging port affect the screen display??