I went through similar the issue a couple of months ago and had no idea of what was going on. Apex customer service is very slow in responding. I had the issue with one of the aquabus cable. Which seem to be the culprit in your case as well. They seem to go bad once in a while and there is no good way to tell which one has gone bad but it screws up everything. Luckily, I was home and not on vacation. Here is what they asked me to do and what I did to solve the issue. . .
Disconnect all aquabus cables. Restart the Apex by connecting one of the energy bars, then go on adding one by one with other bars with aquabus cable. As soon as you connect a bad aquabus either to the energy bar or one of other modules the apex disconnects/stops working. Take that last aquabus out. You might be able to find a new aquabus cable in one of the local store or live without one of the module that is not essential until you get one.
Good luck!