Chosen Solution
After changing the display, my Mac no longer goes into sleep mode (when I close my Mac). I have already done SMC reset. Where can I find the switch?
You likely got the wrong display assembly. Apple moved the magnet within the display on a few models which sets off the hall sensor within the uppercase. Get a metal paperclip and a small magnet. Using the paperclip slide it on the screen face along the edge to locate the magnet. Now carefully fold the display down so you can locate the same location on the uppercase. Now use the magnet sliding it across the uppercase along the edge the location where the display goes out is where the magnet needs to be.
