If you didn't open the faucet to relieve the pressure, the cartridge is pushing up against the clip. Making sure that the valves under the kitchen sink are closed, and open the faucet to relieve the pressure. There is usually a hole at the end of the clip which you can stick an awl into to help removal. Good luck!
P.S. Make sure to note which side of the brass spindle has the notch on it. It should be either facing you, or it should face away. If you put it in wrong, you will reverse the hot and cold. If this happens, simply remove the handle and rotate the spindle 180 degrees to reverse it back.
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If you didn't open the faucet to relieve the pressure, the cartridge is pushing up against the clip. Making sure that the valves under the kitchen sink are closed, and open the faucet to relieve the pressure. There is usually a hole at the end of the clip which you can stick an awl into to help removal. Good luck!
P.S. Make sure to note which side of the brass spindle has the notch on it. It should be either facing you, or it should face away. If you put it in wrong, you will reverse the hot and cold. If this happens, simply remove the handle and rotate the spindle 180 degrees to reverse it back.