Hi,
If you are unsure about whether your tubers are viable, place them in some slightly damp shavings or vermiculite in a plastic bag, close loosely and put on top of your water heater or refrigerator. The gentle bottom heat will help pop the eyes and start the sprouting action. Be sure not to get the material too wet as this will promote rot. Sometimes tubers which have been kept fairly cold will take up to 3 - 4 weeks to pop their eyes. It's really easy to mistake bumps such as old roots and other lumps on a tuber for eyes. I've been doing dahlias for over 30 years and have a little experience in finding viable tubers. Hope this helps.