sgt,
Well I suspect that either the cell, or the power supply inside the ET, has gone south..
Unplug the SWCG from the bottom of the ET and see if the CB will reset.
If you open the top drop-down door where the main PCB is, up against the back wall is the SWCG power supply card. There is a little green "power light" which should be on.
If you have a voltmeter you can measure the DC voltage going to the cell. I think it is normally about 35 VDC. Large plug with four large wires, test between the red and black wires.
If still under warranty, I'd call you pool builder and have them send a Pentair warranty tech out.
Thanks,
Jim R.