As you do not state the model number, I am assuming that this is an electric shredder, is this correct?
If it is then if you have or know someone who has a DMM (Digital MultiMeter -Ohmmeter function) you can test (or get the someone who has one to do the testing) the continuity of the wiring to see if you can isolate where the problem is.
Adequate DMMs are available from most hardware stores for around $10
Ensure that the shredder is totally disconnected from the power supply.
Using the Ohmmeter, connect the meter's two test leads across the power plug's two pins.
When you operate the start button on the shredder the meter should display a reading.
If there is no reading on the meter, ensure that you have set up the meter properly to read Ohms.
If you still get no reading after checking that the meter is setup OK then there is an open circuit in the wiring.
You could try gently flexing the cable where it comes out of the plug to see if you get an intermittent reading when flexing the cable. If you do then a wire is fractured where it leaves the plug and you will have to cut the cable back past the break and re-terminate it onto a new plug (if it is a sealed plug). Also do it at the shredder end where the cable enters the shredder if it didn't show anything at the plug end
If it still shows no reading after doing this then you will need to do point to point testing to find where the problem is.
Start with opening the shredder so that you can access the wiring at the start switch. Connect one test lead of the meter to a pin on the cord plug and then try to find the wire on the start switch by probing with the other meter lead until you get a reading on the meter. If you cannot get a reading at all change the lead on the plug to the other pin and see if you get a reading now.
You should be able to find continuity for both wires between the two pins on the plug and the shredder.
If you only find it for one then a wire is broken between the plug and the shredder. It may be in the plug itself,
in the cable between the plug and the shredder or where it connects into the shredder.
If you find that there is continuity of both the wires between the plug and the shredder, you then need to prove continuity through the switch, (there may also be a safety switch involved in the circuit path) and after the switch, from the switch to the motor and then through the motor itself.
Do all these tests with the power totally removed from the shredder. Do not test on "live" equipment unless you know what you are doing. It can be lethal
Hopefully this is of some help.