Your recourse depends on the grounds for the denial. USCIS must commence removal proceedings. You can either renew your application before an immigration judge if the I-751 was denied for material reasons. If it was only denied on formal grounds, you must re-file with USCIS. Best advice is to see an immigration attorney for an assessment of your case.
I would suggest that you meet with experienced immigration counsel. An immigration attorney would be able to review all of the documents in your initial I-751 for sufficiciency and the resulting denial notice in order to determine your best course of action. The reason for denial is important but there are many other factors to review . I hope this was helpful