i have had this problem many times it seems ,that if your cartridges run empty and the machine ,keep trying to get ink from it ,it will get air in the lines and will not let the ink pass through so you will have to manually prime the dampers till the air comes out the quickest way is to use a syringe and keep looking at the lines and see when the air is out but that is just my printer you could have a bigger problem just try it and see if that works for you. and you need to open the valve when doing the manual prime