There are a few common causes for mismatching inventory quantities between the Source and Destination stores:

- The SKUs no longer match. This is caused by either the Source or Destination store updating and changing the SKUs after the initial sync. Syncio uses the SKU to identify which product/variant to update inventory. It is critical that the SKUs are unique per variant and match between stores.

- Source store has changed the inventory location after syncing. Shopify now allows a store to allocate inventory quantity to different locations. By default, Syncio auto selects an 'ALL LOCATIONS' setting which displays the total quantity across all Source store locations. Syncio also allows the Source store to choose one location for the Destination store to sync inventory from. When there is a change in inventory location, the inventory quantity doesn't automatically resync in the Destination store, the updates will occur upon an event trigger, whether it be from an order or manual adjustment from the Source store. Please contact support to manually resync the entire inventory to the new location quantity.

For Destination stores, you can check the Activity Center to see if any products no longer have SKU matches.