Cant remove the screen from a repaired iPhone

I had this problem. While this may not make any sense put the suction cup near the home button and when you get ready to pull up also push down on it. Don't push down so hard that it isn't going to want to pull up but apply some pressure. This will usually keep the touch screen and the display assembly attached. If that doesn't work try using a blow dryer on low heat at about 6 inches to a foot away and heat up the bottom portion of the touch screen for 10-30 seconds. Then hold the corners of the touch screen down for about a minute or so. Let that sit then for a while and by then the adhesive should have set and you can try using the suction cup again.