Did you bend the battery compartment pins out? The ones on the cap. Also try not tightening the cap so tightly, or cleaning the pins. The pins on the inside are gold-plated, but the ones on the cap are made of tin or something. Also, smacking the strobe around the battery compartment often wakes them up, on the Z-220, 240, and 330.
Or maybe listen to the guys recommending Sea and Sea since Inon seems to be on their way out of business…