How can I eliminate a gap in a refrigerator door gasket?
Most likely the door is out of alignment, and realigning the door is a required step for many gasket replacements. The screws that hold the gasket in place are also the ones holding the door in alignment. You typically loosen the screws that hold the seal with the exception of the corners, inspect the gap and twist the door until it's properly aligned (by pulling or pushing the top/bottom of the door to close the gap), and then tighten all of the screws, rechecking the alignment as you go.