The filter doesn't work a second time because your Clear button is setting the value of the combo box fields to
" " (space) instead of NULL.

So... your Clear button code should be:

Code:
Private Sub Clear_Click()
   Dim intCounter As Integer
   For intCounter = 1 To 4
       Me("Filter" & intCounter) = Null
   Next
    
  'Set Report back to its unfiltered
...