User wants to do Percent Complete billing for a project that has no time and expenses logged to it. However this project is not available in the Create Batch Invoice screen.
This is because the projects that have no time and expenses against them do not show up for billing in the Create Batch Invoice screen unless the project rule Always show in Create Batch Invoice screen is set for them. So you need to set this rule for the project before you can use Percent Complete billing for it. Check Core Help Center for details on Percent Complete billing and project rules.