Some home office/small office shredders have LED bin full sensors while others feature a bin full flap/lever on the bottom side of the shredder head. These sensors can detect if paper has filled the basket. In ideal conditions, the paper shreds will fill until it reaches these sensors or flap, where the "bin full" light will illuminate red, and the shredder will not operate. This is designed to prevent overfilling the basket, which can possibly cause damage to your shredder.
The most common reason for a false reading, where the bin full light comes on but the shredder basket is empty, is simply dirty sensors on the bottom side of the shredder head or the bin full flap/lever is stuck.
To locate the LED sensors, please unplug the unit and pull the basket from the unit. Remove the shredder head from the cabinet if the unit is a personal or small home/office shredder. You will want to pull straight up to remove. The shredder head will be heavy, you may need assistance to do this. On the bottom side of the shredder head near the paper exit area - facing each other - you can locate the sensors which will look like small glass beads or marbles. Wipe these sensors with a soft cloth dampened with rubbing alcohol. Some models (i.e. 225Ci, 225Mi) feature an Ambient Light Basket Full (ALBF) module which emits light into the wastebasket. It determines level of shreds in wastebasket by the light being reflected back from the shreds. The ALBF is located on the underside of the head - in front of the cutting block (on the right). . It is a rectangular area about 1"x2". If you have this style, please wipe with a soft cloth dampened with rubbing alcohol.
There are other units which are designed with a bin full flap/lever rather than electronic bin full sensors. Under the head of the unit, near the exit area, you will see a flap/lever which is about 2" long. There is more than likely some paper bound up around this flap causing it to stick in place or it has become sticky with oil and dust build up. Please tap it a few times to release it and also clean it with a paper towel dampened with rubbing alcohol. Some units feature a flap which extends the width of the cutting block. If your unit has this style of bin full flap, make sure it is still in place and is moving freely.
This will most often solve your problem. It will most likely not be necessary to remove the shredder head each time you clean the sensors, we only ask you to remove it the first time, because the glass sensor(s) are somewhat difficult to locate. You may need to periodically clean the LED sensors along with routine maintenance on the machine.