What would prevent a time or expense submitter from appearing in the project approval queue of a Project Approver?
This is most likely related to the timing of when the project approver was set up on the project. If the Project Approver was set up after the timesheet or expense report was submitted, the timesheet or expense report would not appear in the approval queue even if it does appear in the Timesheet Status report and/or the Manager Approval queue.
Additional information can be found on the online Help Documentation regarding the Timesheet Status report (see link below).
Below is an excerpt from that Help page:
Note regarding pending Project Approvals. On occasion, a project approver is added to a project after the timesheet was originally submitted. In these cases, the Timesheet Status report may erroneously reflect a pending approval for that new project approver that is not actually pending (that is, the project approver will not see any pending approvals in their actual project approval queue for that particular timesheet). This discrepancy is due to how the Timesheet Status report derives potential pending approvals that may not yet exist in a project approver's queue (i.e., in situations such as "approves first"). As such, it is possible to encounter these "phantom" pending project approvals. Once these timesheets have had the other Manager, Project Approver, and Customer approvals satisfied, the timesheets status will graduate to COMPLETED and the phantom project approval will no longer appear on the Timesheet Status report.