Manager is not able to assign a Direct Report as Delegate

Issue Summary

Single user is unable to assign direct reports as delegates for time approval.
User A (manager) is trying to assign User B (direct report) as Delegate for time approval but User B’s name is not appearing in the dropdown list.
Even with all Time Tracking roles enabled for both users, User B does not populate as an option.
User B is a direct report for User A. None of User A's other direct reports are selectable for User A as Delegates, either.

This is reproducible on Data Center: yes

Steps to Reproduce

1. Step 1. Confirmed Can approve time for any time tracker is set in Administration -> Time Tracking -> Time Approvers. Confirmed all Time Tracking roles enabled for both users.
2. Step 2. User A (manager) is trying to assign User B (direct report) as Delegate for time approval but User B’s name is not appearing in the dropdown list.

Additional information

• Checked to confirm that User A was not a delegate for another user.
• Confirmed User B and User A accounts have Time Approval roles in Edit User pages
• Confirmed User A and User B are both in the same Portfolio
• Other users that are managers (aside from User A) reported that they can assign their direct reports as Delegates as expected.

Expected Results

User B's name is appearing in the dropdown list when the manager tries to assign user (direct report)

Actual Results

User A (manager) is trying to assign User B (direct report) as Delegate for time approval but User B’s name is not appearing in the dropdown list.

Workaround

Required, if there is no workaround please state