What kind of certificate are you talking about?
Is this a software licensing certificate? If so, it's best to contact your vendor and find out what the hold-up is.
If this is a certification certificate, it can take a couple of months for it to arrive. If it hasn't been that long, its best to wait it out. If you really need something sooner than that or it's really overdue, you can login to the Certification Tracking System at http://www.cisco.com/go/certifications/login, go to Certification Fulfillment under Certifications on the left-hand menu and order printed or electronic copies from there.
