The main cause for this is you are trying to book stock out of a location where the product is not in stock.
This could be because the system defaults the location to the Default Pick Location of the product if you have set this.
To view where the stock is located:
Click Products then Overview.
Search for the product.
Click Actions then Manage Inventory.
Then click the Unallocated tab.
Make sure the location you are trying to book out from also matches this.
Best Before Dates/ Batches!
If you have enabled best-before date or batch code tracking, you will need to make sure you provide a matching value for these as well when booking stock out (This also includes any unnecessary spaces).
Quarantined Stock
If stock is currently in Quarantine, please Un-quarantine it before trying to book out the stock. If the stock is still in Quarantine when trying to book out, the error will show.
Note: If you are still facing issues with this, please raise a new case online and reference the title of this article.