If your shredder is still jammed after trying these steps for 30 minutes, it may be time for a replacement. Entry-level shredders often cost less than the labor of professional repair.

Sometimes the "jam" isn't a mechanical failure but a safety sensor trigger. Paper Shredders - Fixing Jams & Maintenance

If you have cleared all visible paper, oiled the gears, and let the motor cool, but the shredder still won't grab paper or makes a grinding noise without cutting, the plastic gears inside the motor casing may have stripped. At this point, it is usually cheaper to replace the unit than to repair it.