if it is the cassette style toilet, you have possibly got a blocked filter at the base of the pump, access it by taking out your toilet roll holder. your pump is below this. if there is evidence of brown furring in your tank. you will need to empty the tank, clean it, remove the pump retaining screw and inspect. if the fan at the base of the pump does not turn manually, replace it, as it it siezed or due to seize. Lee- service technician.
Lee Middleton
October 2008