Macro not trigger on cell value change

Your codes and references:-

Set myCopy = inputWks.Range("UpdateEntry")

UpdateEntry=Input!$C$3:$C$18

myCopy.Copy

UpdateEntry is a single Cell? It consist 15 cells.

Change event code

If Target.Cells.Count > 1 Then Exit Sub

According to above line Pasting should happen in single cell, but your copy range consist 15 cells and the if statement will end the code.