It can still be worth asking, but the process varies by firm and office, so avoid assuming the referral will automatically attach to an existing application.

Tell the consultant that you have already applied and ask whether their referral system allows a post-submission referral or recruiter note.

If they are willing, provide the exact role, office, application date, and email used in the application so the record can be matched.

Do not withdraw and resubmit unless the firm specifically instructs you to do so. The main value is making sure the referral reaches recruiting without creating duplicate applications.

I have seen this go badly when people keep adding detail after the answer is already clear. Shorter was better in my mocks.