If the fan is rotating but air is not being extracted then there's a problem with the airway - blocked or fallen apart - one or the other.
If the fan is not rotating then there's either a problem with the fan itself (broken) or a problem with the power supply - fuse - wire - switch - control board perhaps.
Nobody here can diagnose the precise reason with any accuracy - you will need to do that yourself or call in somebody to help you - neighbour or specialist engineer.
It often helps to say the make and model of the appliance and in this case if the fan is actually turning as it should - can you hear it or not?
Good luck...
S Hawking
September 2014
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