My initial tests showed that the converter was not able to trigger the strobe even though all LED lights were flashing correctly. Just before I was about to send the the unit back, I thought I'd do another test and boom, it was working again.
There was no explanation for this sudden revival as I'd tested it with 2 different camera systems and 3 different cameras. Even Matthias and Chris said send it back (Firmware upgrades are all done only in-house at HW).
So what changed? A few days before, I'd reset the 1DsMkII completely since I had difficulty with the AF Assist activation with a 580EX. When I connected this camera to the Seacam housing and the HW, it fired! I promptly tested with the 1D2N and 1DsMkIII and suddenly they all worked.
The eTTL functions as planned. Canon eTTL is funkier to work with but it works. As to what caused the change, I'd put it down to crossed wires with gremlins and I forgot to sacrifice that lamb/human/chicken.
I may still send it back to get the firmware updated and the plastic tube replaced later. but for now, it works... again.
Issues with the HW are
1. firmware can only be updated in Germany.
2. My unit works intermittently.
3. I now keep a small pack of silica gel inside the tube. The o-rings tend to collect water and if you remove it to clean, the moisture is inside the tube and will stay there.
4. Fragility. Removing the unit from the tube makes me nervous from cracking the plastic tube, plus you need to replace due to use. If there is an alloy replacement, I'd recommend that if you are all thumbs like me.
5. No rear curtain.