Suggestion for testing the HC-110 (I've never seen the stuff go bad as concentrate, but I suppose it's possible it was defective from the factory): Mix up a tray or beaker of Dilution B and drop a sacrificial film (a scrap of 35 mm leader or whatever) into it, in the light. At any reasonable room temperature, it should fully darken in a matter of a minute or two. If it doesn't, something is very, very wrong with your developer, and your dealer or Kodak should replace it as defective.
FWIW, I've used HC-110 30 years ago, for both film and paper, and I've used it since coming back to photography (not quite two years since I developed my own again). I've used year-old syrup from a partially filled small bottle (I divided up the pint when I opened it) that sat for more than four months, including a couple weeks in a van in direct sun in North Carolina summer weather, and it worked exactly the same as the first mix from a new bottle. HC-110 is the only other commercial developer with similar lasting power to Rodinal.
Are you certain you aren't mixing stock solution in concentrate proportions? That would give you severe underdevelopment -- but still shouldn't give completely clear negatives; strong highlights should at least give a visible ghost.