So I filled a medicine dosing syringe with 91% isopropyl, squeezed the Dark Matter bottle, and squirted alcohol into it. It worked! I reconstituted it, and it works.
Not positive the metering is accurate, but it seems good. The drops have the black powder in them.
I haven’t heard anyone else complain about theirs drying up, so maybe I just got a bottle that doesn’t seal properly. But if yours dries out, try putting some alcohol back into the bottle.