Time Entries from Projects not able to Submit For Customer Approval

Time Entries from Projects not able to Submit For Customer Approval

Hello, 

I have a project in Projects where I have time entries that have synced with Books. They are all billable, but when I try and "Submit For Customer Approval", I get this error:

Some of the time entries you’ve selected cannot be included in the Customer Approval as they:

  • were already invoiced or associated with another Customer Approval
  • are non-billable time entries
  • are time entries of projects without Customer Approval

We recommend that you skip these time entries and create a Customer Approval with the other time entries.

They have not been associated with another Customer Approval and are indeed Billable time entries. The option for Customer Approval seems to be the issue, but I cannot find that in either Projects or Books.

Help would be appreciated.