The 'magic module' as I shall call it has worked! The 'generate' light is on and bubbles are leaving the cell. A big THANK YOU to CircuPool for being so fast and friendly!
Going to chime in here with my recent experience. My 3-year-old Circupool RJ45+ was working fine until a week ago when stopped working, frozen on "Cell Connection" (just to be clear, when working, it shows "Cell Connection" for a few seconds after power on, but then quickly switches to "RJ series" and then normal operation. When broken, it stops on "Cell Connection" and will not advance).
I called Circupool and they suggested reconnecting everything, checking for dirt and bad pins in the connector, etc. I had already done all that but I did it again and no joy.
So they shipped me the magic module. They charged me ~$40 which I assume is list price pro-rated by the 3 years I've owned it. Would've been nice if the fix were free but $40 isn't bad. UPS chose to send it via the scenic route (Houston to New Jersey to Chicago to Tucson) so it took a few days longer to arrive than it should've. Obviously not Circupool's fault.
Once the part arrived it took me about 5 minutes to install and imagine my surprise when it actually worked!
No, I don't know what's in the magic module and I didn't ask. It is interesting that they have a fix ready for this - kind of looks like a design flaw, probably a marginal voltage threshold somewhere. But hey, it works now, so I'm happy.