Start by talking to the auditor and see what he can tell you about the deficiency. Although he can't answer them for you, he should be able to tell you more than just that they are rejected.
One of the best guidance documents available for answering audit nonconformances is the ANAB "Heads Up" 137. It can be found on the ANAB web site:
Be aware that the audience is slightly different. It is how ANAB wants Certification Bodies (Registrars) to answer nonconformances written by ANAB against the Certification Bodies. The principles are the same though.
Something to keep in mind is that they expect to see a good correction (action taken to overcome the nonconformance), an appropriate root cause, one that truly gets to the root, not just one of the contributing causes, and an appropriate corrective action (action taken to overcome the CAUSE of the nonconformance). If the root cause is perceived as not deep enough, it will be rejected. If the correction and corrective action are nearly the same, that shows either an inadequate root cause or a misunderstanding as to what the difference is, and will always be rejected.
Read the "Heads Up" 137 and see if it helps.