Wow that is a bit of a shocker. DP makes some good shit. If you said White label seeds then I wouldn't be too surprised. Typically people that buy DP stuff either have problems with hermies or mutations with some of their strains and a couple of their fem seeds, but aside for that their stuff is pretty good.
For the most part though their shit usually pops open in 48 hours or less. Hell a buddy of mine had a chipped DP Power Plant seed (25% of the seed was missing) and that fucker popped open like a normal seed in 12 hours. You must have got a bad batch or screwed up germing it. What method did you use and how long have you been germing? I wouldn't call t his a total failure until a weeks past.
Your seeds could have a hard outer shell. Try placing sand paper in a match box and shake the seeds around. This will cause microcuts in the shell and help speed up germination for seeds with a hard shell. I'd try that before I said these seeds were a total failure.