Yes, in many cases you can reopen a denied immigration case. It depends on why it was denied and how long ago it happened.

If your case was denied for missing a hearing, you may still reopen then you must explain the reason like medical emergencies or lack of notice.

If your case was denied in court, you may also file an appeal then it goes to the Board of Immigration Appeals (BIA), not USCIS.

You must explain clearly why the decision should be reopened and this includes writing a statement and attaching supporting documents

You must file a motion to reopen or motion to reconsider. These are official legal requests submitted to USCIS or the immigration court.