Display All Time Entries in Transactions > Customers > Invoice Billable Customers

Please check to make sure Charge-Based Billing is unchecked under Setup > Company > Enable Features, Transactions tab, Billing section.

With this feature checked, the if the Billing Type of the project is empty or Charge-Based, the time entries for this project will not show up on Transactions > Customers > Invoice Billable Customers. Only time entries with projects that has billing type of Fixed Bid, Interval, Fixed Bid, Milestone and Time and Materials will show up on that page.