fuel tap?

i took the carb off to clean the jets on my derbi senda 50 2004, i put the carb back on after cleaning it and now there is no fuel running throught the tap. there is no, on/off switch for the tap and the pipe and filter in the tank are not blocked, you can blow air through the fuel pipe into the tank but you can not suck fuel through?? can anyone help?? Regards Jay