Why is my S23 ultra's screen dark

Yesterday I replaced the busted screen in my S23 Ultra and my phone powered right up but then I noticed things like my Spen no longer worked and when I would jar my phone even the slightest it would say restarting but never actually restarted, well that's when I noticed, due to my inexperience wih replacing screen and frame myself, [for the first time ever], that I had missed some screws so feeling a bit more confident with now having a little better understanding of how everything goes together inside my phone, I began removing the back once more so I could put the missing screws back where they should've been to begin with but then when I tried powering it on before sealing it back up again all I get is a logo written in yellow that says "Samsung, Powered By Knox" for approximately 3 seconds and then the screen goes dark but it is actually turned on. Can anyone help?