List boxes do not have an "ALL" selection. If you want all values in a list box for your search, leave them all unselected. Matrix assumes you want all values in your search, unless you specifically click to select certain values (thereby excluding those not selected).
For example, if you do not make a selection for Status, Matrix will return all statuses in your search. If you click to highlight "Active" but leave all other statuses unhighlighted, Matrix will only return Active listings.
If you have already selected a value but really want "ALL", then hold down the Ctrl key and click on the selected value to deselect it.
When ALL items are selected, the background of the select box will be white. If one or more items are selected, the background is light blue