Once the Multi-Location Inventory feature is enabled, users are required to distribute inventory before entering any inventory transactions. To do this, navigate to Transactions > Inventory > Distribute Inventory.
1. Item A Last Transaction = Invoice dated 01/10/2015.
2. Item B Last Transaction = Invoice dated 12/31/2014.
NOTE: If you turn on MLI and distribute inventory the same day (01/14/2015), both items will appear in the Inventory Distribution Page. But if you turn on MLI today and date the Inventory Distribution for 01/09/2015, only Item B will appear since there are transactions for Item A dated after the Inventory distribution date.
If after checking all information above and the items still didn't appear, this might be a probable defect.