Sage Intacct sync error: Use of empty Entity is invalid. A valid Multi-Entity Entity must be specified.

Why the sync error occurs

This error occurs when there's a $0 line item on a bill that's syncing to Sage Intacct, or there's a line item that has an amount, but not a quantity.

How to fix the sync error

Remove any $0 line items from the bill, or add a quantity to any line items missing a quantity and sync again.