I think that Gene's experience may have been with developing 120 roll film where you need 500 ml to process a single roll. In that case you need two packets to make up 500 ml. But a single roll of 35mm should only need 250 ml of developer and one packet makes that much. Outside of that possible error of mixing it at half strength, I cant think of anything that would lead to really low contrast results. Maybe you got a bum lot of technidol? Try another roll of film and see if it was a one time problem. If so chalk it up to a random glitch. If not try another lot of technidol.(posted 9245 days ago)Another developer you might want to try is TD-3 from Photographers Formulary . I just bought it for the first time and can't tell you how it works in my hands yet, but others seem to like it quite well. Plus you get a true speed increase to EI50 with it. It's a lot cheaper too.
Good luck.