The Inventory Activity report is used for end of month inventory reporting and is run by date range. The inventory displayed will be as of that specific date range.
Select a date range and click the "Go" button to see the inventory activity in the search interval.
Click on "More Options" to narrow your search by a Specific Sku, Subinventory, or by SKUS with Activity.
Uncheck "Only Show Skus with Activity" to get a report of inventory that has not moved during the date range selected.