I appreciate your response and the link to the Valley products. My cartridge is the V6680. I tried to insert a picture of my faucet into my first posting, but it didn’t work.
Yes, water does flow (when I turn it on beneath the sink). It does seem therefore that I may have inserted the cartridge incorrectly, but I have no idea how I can have done that. The cartridge has a plastic tab on the left side which fits into a detente on the metal base. With that in place, and the cap screwed on over it, it can fit in only one way. My next step is to replace the rubber inserts that fit into the hot and cold holes on the bottom of the base. I don’t really think this can be the cause of the problem, but at least I’ll try.
Thanks.