Problem running Jebao powerhead off Apex - not sure what's broken

[Delphinus]

Here's my headache this week ... usually I'm pretty good at diagnosis but this one has me stumped. I would welcome any suggestions at this point..

I have a single Jebao RW-20 in my tank alongside two Tunze 6105's, all controlled by my Apex (I run through several profiles over the course of a day giving some really neat flow effects.)

Anyhow, I noticed that the Jebao was no longer turning on. Given that these are expected to have shorter operational lifespans, I assumed the pump had given up and it was time replace it.

So I went to Concept and bought a new one. Came home, plugged it in, and, nadda. Ummmm ok. So, that's strange?

Tried the one again but on its own controller. Started up and ran just fine.

Conclusion: The Apex to Jebao controller adapter must be the culprit.

Go back to Concepts. Return the new powerhead. Buy a new adapter. Go home and plug it in and....... nope, powerhead still doesn't start up.

Conclusion: maybe the powerhead is no good after all.

Back to Concepts. Return the new adapter. Buy yet another powerhead. Still no go.

Conclusion: The Apex must be the problem?

To test the Apex, I plug the Tunzes into the port. But they run fine. Ok, I guess the good news is that it ISN'T the Apex?

I try the Jebao on the other port, still no go. Connect up an unused VDM module I have, try the Jebao on there, and still no go.

Um ... ok. Maybe it's the cable? I test each pin on the cable and each wire shows connectivity. I try mixing and matching pins to see if there's a short, and, it appears the cable is fine.

So here is where I'm left:
- The Apex appears to be working correctly.
- The cable to the adapter appears to be working correctly.
- The Jebao powerheads appear to work correctly when on their own controller.

What exactly am I overlooking?

I have now made 3 trips to Concept to return gear and exchange. I am highly reluctant to make a 4th trip and ask for yet another equipment exchange until I have some better idea what exactly I need to ask for.

Any suggestions?

PS. I suppose it wouldn't hurt to make a new cable anyhow even if the old one tested out fine. It is just a small piece of cat5 network cable so maybe those wee tiny little wires aren't enough?? But seriously given the fact the port is meant for network cable connectors, why wouldn't a regular network cable work? (And it tested out fine with a multimeter, so I don't know??????????)