Have a look at this thread: iPad Mini Home Button Not Working After Digitizer Replacement
the answer was given by GtechRepair: "The easiest solution Is to go back to the old screen at the bottom where the Home button is located, There you will see two pieces of fabric tape, The one closest to the home button will be layered over a clear piece of tape, try to remove them together, use x acto knife to lift up corner, then a good pair of tweezers to peel it off.
Perform the same procedure To the fabric tape to the left, Then place both pieces down on your new digitizer, In the same place that they were in on the original. This should solve your problem 100%."
these black tapes go here: