Are they still dried out, or have they plumped up a bit? Was the soil damp?
I take it they are outside C3k. It's not warm enough outdoors for them to get going yet. Bring them inside if you can and you should see signs of life in a week or two.
Dahlias are really tropical plants so hate the cold and wet of our British climate. We can only grow them because they are really fast growers so can actually be grown from seed to bloom in about 5 months.
Hi C3K Ive had mine planted in pots in the garage window for over 4 weeks they just showed there first sprouts yesterday at long last
Tubers can surprise you, but patience is definitely called for. The last of mine just sprouted after almost 2 months. The main thing is not to rot them while you wait. And resist the urge to root around to see what's happening. Next year try planting with the tops of the tubers actually exposed-especially good if you want to make cuttings.