Version
6.5 Update 5, not the version-specific
Issue
When selling any item that is zero price, and putting a zero value into the order, then cannot complete the sale.
Observations
Allow zero price is enabled at the enterprise, and this event has been replicated to the store.
Resolution
Mark that Item as Zero at the product screen to fix the issue. Below is the screenshot for the same:
This KB article concludes here.