If you run either the Historic Inventory Levels or Historic Inventory Breakdown reports and notice that some products show a blank value, follow the steps below:
Click Clients then Overview.
Locate the client for whom you want to run the report.
Click Actions then Edit.
Go to the Defaults tab.
Enable Record Inventory Levels & Stock Value Daily to begin building the historical record.
This will start recording inventory levels daily from the moment it's turned on. If the values were previously blank, it’s likely because this setting was activated after the date you are reviewing for stock levels.