The 04 series didn't have a check valve ball in the intake, or at least mine didn't.
That's an old filter, at least 10 years old probably. There's alot of things that could be the issue. Nothing wrong with the 04 series I just retired a 104 that was like 15 years old.
Make sure the canister filter is full of water first, check the hoses for leaks, make sure they aren't drawing air. Check the main oring, lube it with silicone gresse. Check the impeller for damage, make sure it's seated right. Try putting the outlet above the water level so it can purge air