Lorli,
My guess would be soil temp like Xeramtheum said above. They really like warm soil, and even here in Florida, in the greenhouse mine don't usually wake up till May. I place them where the pots will get really warm in the spring.
When I store them over the winter, I remove the soil from around the top, sides and shake the soil so it's loose around the roots, then store them pot and all in a cool DRY place. With the little tubers I just store them in a covered box with a little dry peat in the bottom. But I have seen them stored in a greenhouse just laying out in a tray. A bit of humidity is good, perhaps if it was inside the air got too dry and the tuber just completely dried out ??
At this point your probably looking at next spring unless you have a really nice room with plenty of light, warmth and humidity. Ours go dormant here around mid October. Even if brought into the greenhouse.
You might try putting them in your warmest spot you can find in the spring. Only "mist" the surface enough to keep the soil from becoming a dust bowl, but no watering till they sprout, and show their leaves.
Here's a couple pics of some of A. bulbifer babies taken on 6/22/2014. These were about the size of a standard marble. At this point I started them on a dilute fertilizer. I use a 20/20/20 - 1/4 strength till the leaves unfurl, then I bump to 1/2 strength till they have a little growth on them.
Two separate trays, all planted at the same time. You can see the difference in emerging, and in two of the cells on the pic on right they hadn't even emerged yet.
