Agency Recruiters work with tight deadlines, important client needs, unreliable candidates (at times!), and various circumstances out of their control. In this high-pressure, fast-paced environment, the interviewer wants to know how you react when failures occur or you fall short. Nobody is perfect. Show the interviewer that you get back up and try again, never giving up in the face of perceived failure. The best Agency Recruiters have grit, and the interviewer wants to see that this is a characteristic you possess.
Since this question is posed as a 'tell me about a time when' query, approach your answer using a story-based example using the STAR framework (Situation, Task, Action, Result). This answer framework will allow you to deliver an engaging story that is easy to understand.
