I hadn't used my water kefir grains in a looooong time. Like, since last summer I think. But I've had a sore throat and I just felt like some juice kefir so I hauled them out (I stored them in filtered water in the fridge) and plunked them into some (expensive) unfiltered apple juice. And for a day and a half, nothing happened. I mentally called them dead, but I didn't get around to emptying out the container for another half-day, and then - miracle of miracles! - little bubbles started to form on top, and I could see a small amount of fizzing at the bottom. This morning it's going pretty well, and it smells right. So they weren't dead, just sleeping!
I am posting this in case anyone else has similar troubles... just give them a couple of days before you give up on them!
Postpartum doula & certified breastfeeding educator, mama to an amazing girl (11/05) and a wee little boy (3/13).