It may be a lake that crappies are not active in the real dark portion of the 24 hour day during the cold months. Maybe the primary food source in that for crappies are not active in the dark in that body of water. Unless you have a camera you could mistakenly think a school of shiners is a school of crappies….be certain you are actually marking crappies.
The no live bait thing might cripple you though as crappies do like their minnows. Can’t you use the waxies or spikes? Red Spikes would be a great teaser for crappies when fished on a jig. The Gulp 1″ minnows would be my approach and if the fish are fussy on size just cut the minnow in half and use the tail end.
Steve Root has mentioned crappies hitting in a real narrow window of activity and that may well be the case on the lake you’re on.
Another thought for you is to start early as you say you have been doing but fish right under the ice, like only a foot down below where the ice stops. Any fish up that high will be feeding and your electronics will not pick it up. In winter some of the crappie’s forage dies and will float up to the bottom of the ice sheet and crappies will rise and pick the stuff off the bottom of the ice, but if you’re approaching them in this way don’t use lights and tread lightly. Drill a mess of holes and clean as you cut, then quietly walk back to the first hole and start fishing.
You haven’t mentioned exactly what you’re dropping down the hole but glow red jigs seemed to do me the best under the ice when poking around for crappies. And I always preferred a vertical type of jig and presentation using a glow red 1/16 ounce Forage Minnow. Glow Red Jigging Demons worked great too. I’d use a small white active plastic tail on one of the hooks when I wasn’t using the Gulp 1″ minnows. If you interest in your bait offering but they won’t take it, try moving up in bait size. Try the smallest of the Rippin Raps or a larger jig/plastic. Just because its cold doesn’t mean that crappies will not hit on a bait way larger than you are accustomed to using.