Holgas are made to be assembled very cheaply, NOT to be taken apart easily (if at all). But, some take them apart for various reasons. It sounded like you checked the hot shoe for continuity, and it seemed to be ok. Do you (or a friend) have another model flash you can try, to see if the problem could be using the Holga and your particular flash unit? I dont know how to get the winding knob off, and others indicate you can break something if you do it wrong (or even do it at all). It's not a 50yr old Leica or some other family heirloom, so you wont be out a lot if you break it, but be very careful if you do.
Remember, things are a lot easier to hack than to UN-hack.
Paul