At end of day everything needs to be working since pool is less than yr old. If I can fix fairly easily & avoid warranty service call out, I’m willing to fix it (or at least trace issue down to brass tacks before I reach out to Pentair).That is because you disconnected the heater from the ET. Now we know the heater is working and that is not the problem. The problem is with the control wire to the ET or the heater relay in the ET.
You have your heater working now. You want to dig into the ET panel?