Yellow light comes on

It's designed to only start in neutral. If the reverse light is on, it will not start with the button.

Likely the unit is detecting a reverse direction. Could be the reverse switch, adjustment, or debris. Try using the ROS position on the ignition switch. If the problem goes away then it is definitely reverse operation related and further diagnosis of reverse detection required.

I tried the DIY service and repair manuals from a website and it actually helped me repair
transmission problem in my jcb 3cx site-master. it wont move forward or reverse, engine is good both solenoids for forward and reverse work.
I don't have much technical knowledge but I just followed it step-wise, and works perfect! got it from www.reliable-store.com

Link to the manual
Fellowes Shredder Manuals

Keep driving & you won't have to worry
about the motor anymore

Hi,

Ensure the wastebasket is empty then move power switch to the REVERSE position. This will reverse the jammed paper out of the shredder. If shredder jams again, alternate control switch slowly between REVERSE and AUTO (l) positions to attempt to move jammed paper completely through the shredder. If the shredder jams in reverse mode, move the switch to AUTO (l), depress the manual forward button located on the center of the shredder head and allow to run for five seconds. If jam does not clear, move switch to REVERSE again and allow to run for five seconds.

Repeat this process until jam is cleared. If necessary, turn off shredder and use care to grasp the paper and carefully pull out to clear jam. Once cleared, move switch to AUTO (l) to continue shredding. The jamming may be happening because the cutting cylinder needs to be oiled.

Follow instructions to oil your shredder;

To keep your shredder in top condition, the cutting blades need to be oiled every so often (for frequency, please refer to your owner's manual). We recommend using Powershred® Lubricant or a vegetable-based oil (such as corn or canola) in a non-aerosol container with an extension nozzle.

Caution: Never use flammable synthetic oil, petroleum-based, or aerosol lubricants to oil the cutting blades. Some agents may combust, causing serious injury. NEVER USE WD40.

1. Depress and hold the reverse button down.
2. Put the tip of the oil bottle in the paper entry and make one or two sweeps the length of the entry while squeezing the oil bottle.
3. Move the power switch to Auto (I) position, or depress the manual forward button (depending on model of shredder) and allow the blades to run at least three seconds.
4. Move the power switch to Reverse (R) position and allow it to run for at least three seconds.
5. Repeat steps three and four above at least three time.

Regards.

Chances are it's over heated.
Ensure the wastebasket is empty then move power switch to the REVERSE position. This will reverse the jammed paper out of the shredder. If shredder jams again, alternate control switch slowly between REVERSE and AUTO (l) positions to attempt to move jammed paper completely through the shredder. If the shredder jams in reverse mode, move the switch to AUTO (l), depress the manual forward button located on the center of the shredder head and allow to run for five seconds. If jam does not clear, move switch to REVERSE again and allow to run for five seconds. Repeat this process until jam is cleared. If necessary, turn off shredder and use care to grasp the paper and carefully pull out to clear jam. Once cleared, move switch to AUTO (l) to continue shredding. The jamming may be happening because the cutting cylinder needs to be oiled. See oiling instructions below.
From fellow's website: http://www.fellowes.com/fellowes/site/support/support_troubleshooting.aspx#jammed

I tried the DIY service and repair manuals from a website and it actually helped me repair transmission problem in my jcb 3cx site-master. it wont move forward or reverse, engine is good both solenoids for
forward and reverse work.
I don't have much technical knowledge but I just followed it step-wise, and works perfect! got it from www.reliable-store.com

Check the calipers for sticking, also check the lever where the e-brake cable connects to and makes sure the lever operates smoothly. You may need an assistant to operate the e-brake.

Sounds like the reverse mechanism has jammed...either with lint or lack of use and oil/lint has frozen the mechanism.
Unplug the machine and remove the base. Clean all the lint with small brush and vacuum.
Try the reverse lever to see where the connecting rods are and identify the collar around the bottom shaft....try to move manually, use a little lubricant where the collar moves on the shaft.
In extreme cases it may take several applications over several days to rectify this, but as this is only 3 years old, should respond quickly