User initially had a project set to the Hourly contract and changed it to Recurring. After updating, the invoice shows a Net Bill of $0. Creating invoices for new projects with the Recurring contract type works fine, but this project shows zero invoice amount.
The issue might be caused by an already existing invoice related to the project based on the previous contract type. In that case, the new invoice will result in a net bill of $0 because an invoice for the current month already exists. The only solution is to update the Net Bill manually.