Assuming you have great water pressure going into the valve, make sure the valve stops are open. Use a flat head screwdriver and screwing them out toward you to OPEN. (Screwing them inward will close them) Any position in the middle will limit water flow.
If the valve was not soldered to the piping, before installing run some air through the valve (with stop valves open and cartridge removed). It could be that leftover material is stuck in the valve from production. While this is not common, it is possible. This can also help to know if the valve body itself is defective if the air doesn’t pass. It is always recommended to flush the valve prior to finishing installation and even more when replacing the cartridge as left over debris inside can clog the new cartridge or the valve body.