Player Detection isn't working

I am watching this tutorial https://www.youtube.com/watch?v=S8lMTwSRoRg&t=3393s and i am at 55:16 and i followed every single step and it doesnt dectect my player please help i have been stuck in tgis part for almost an hour please help

We would need to see your code regarding collision and or gravity as that is what you linked in the video. I can only take a wild guess and say your collision layers may not match and you pass through the floor?