Well, what can go wrong? If stored wet the cartridge can mildew, but if dried out prior to storage then there's nothing to go "bad." O-rings can dry out so they should be inspected for cracks or hardening. If they're okay, then lube with silicone grease and reassemble. If the pump doesn't allow any air into the system and water doesn't leak out of any joints, I'll speculate everything is okay as is.

Cheers,

Rick
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--Rick