The shredder will run in reverse but will not run foreward.

If the motor will not run, then probably there's paper clogged in the shredder. Turn over the shredder, after unplugging the power cord, and remove the papers.

If the motor will run but not shredding any paper, then the drive gear has broken teeth. This is not usually worth fixing.
Hope this helps.

It's a tedious process to clean it out. Most auto switch shredders use either a tiny little lever or an optical sensor in the paper feed slot. Usually removing the shred head, picking all the paper out and blasting all the dust out with air will clean it up. Then run a few sheets of paper with shredder lubricant (basically clean mineral oil) to oil the blades and it should be good to go again. Just be careful cleaning that cutting head. I've donated many drops of blood to office equipment over the years.

Most likely the cutters are still stuffed with paper shreds and needs to be dismantled and cleaned

Simple to solve!
Get some longnose pliers or strong tweezers.
Unplug the beast. You do not want to shred your finger nails, or your fingers.
Flip the mechanical part upside down. You will find small pieces of papers near the rollers. Pull them out with tweezers or pliers.
Keep hands out of harm\'s way, plug shredder and make it run in reverse for 1/10 of a second.
Unplug and remove more paper impacted in between rollers.
Repeat last two steps until no paper is seen by the rollers.
Plug and continue shredding your papers

Piece of advice. Do not shred your credit cards in shredder. Scissors are cheaper and do not mess your shredder!

I got mine to work by running it on reverse for a moment then sliding it to auto. It stopped. Then I did it again. This time auto ran just for a second then stopped. I did it a third time but I had a sheet of paper ready in the feeder. Ran on reverse. Slid it to auto and it took the paper and shred it. I did it a fourth time. Reverse slide auto and feed shred the paper. Fifth time Auto shred the paper without reverse. :)

I just had this problem with my shredder. I think the problem started with a bin that was full. Running the shredder in reverse resulted in shredded paper being pulled up into the slot used to feed paper into the shredder. Some of this shredded paper was blocking the little plastic tab that activates the switch when paper is inserted, so the shredder would no longer start when paper was inserted. I emptied the bin and removed the shredded paper from the feed slot, being careful not to break the plastic "sensor" while removing the paper from under it. The shredder works fine now.

I just had this problem with my shredder. I think the problem started with a bin that was full. Running the shredder in reverse resulted in shredded paper being pulled up into the slot used to feed paper into the shredder. Some of this shredded paper was blocking the little plastic tab that activates the switch when paper is inserted, so the shredder would no longer start when paper was inserted. I emptied the bin and removed the shredded paper from the feed slot, being careful not to break the plastic "sensor" while removing the paper from under it. The shredder works fine now.

The "eyes" may be dirty....unplug machine; try cleaning the eyes in the middle of the paper slot with a dry cloth. Plug back in a try again.

check and see if there is a jam of paper inside the unit or around the sensors

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sounds like you probally have a stripped or broken drive gear. Contact manufacturer for parts availability.