In all of the reading I have been able to find, it seems that Heinrich is saying that it is a problem with only getting the preflash fromt the strobe - and must be attributed to the cable.
The TTL line of your strobe is not properly connected to the converter. What you see is the preflash. Due to the fact that the flash does a full dump (no TTL signal) the strobe is not ready for the mainflash a few milliseconds afterwards. The results are a black picture. Check continuity of all cables and make sure you have good contacts. The actual timing of the flash is not influenced from our converters at all!
Aquatica 20D Housing (with dual Nikonos style connectors)
Heinrich eTTL converter
Ikelite DS-160 strobe
Iklelite 4104.62 synch cord
Thanks in advance.