There is Plenty of Inventory to Allocate but the System Only Allocates Some.

This is a common issue that happens on Sales Orders and Transfer Orders. Most likely, the inventory either is in a different Unit of Measure or is allocated to other Sales Orders/Transfer Orders already.

To understand the inventory and its allocations, review the Item Availability Status Report page.

Filter the view by Item No. and Warehouse to see the inventory and its allocations by Item and Units of Measure.

Click the Allocated field to see all underlying transactions.

Then, you can then navigate to the actual transactions to update or remove allocations.