challenge shredder ps062/b?

i have got a challenge shredder i bought from argos and it will not feed its model number is ps062/b its not that old i cant take it backas i dont have a reciete for it in where the shredder is the centre bit is missing which i think is where the signal is given to start shredding i dont want to throw it out as it has been doing a good job for me but would i be cheaper to buy a new one hope you can help thanks