1. All items on the Sales Order have been fulfilled.
2. Status of the Sales Order is Pending Billing.
3. Bill button is showing on the Sales Order.
4. The Sales Order does not show up under Transactions > Sales > Invoice Sales Orders even when there are no filters set on the page.
Cause: The customer is marked as Inactive.
Open the customer record in Edit mode.
Go to System Information tab.
Unmark the Inactive box.
Make sure that none of the items on the order is marked Inactive.
Else, the system will generate a prompt "This transaction uses the following inactive items, You should remove these items before saving if you do not want their balances to change."