E13 is not covered in the Manual because it is rare and not very serviceable. It indicates an electrical fault on the PC Board, typically a voltage overload or shortfall. The cause could be a storm or Utility repair issue, that causes SunPump to shut down.
Fix 1. Turn the power of on the unit and breaker for at least 10 minutes (so the refrigerant pressures balance), then turn back on. This should clear the message and allow the unit to restart if the system is OK.
Fix 2. Take a picture of the board, and close up picture of the serial number, so we can identify the PBC model. Alternatively, write it down and post in a ticket here, so we can locate the same Board. We will courier a replacement board to swap out, on free warranty coverage.
The swap is not difficult but does require attention to detail with labeling each wire to the the original location. Do not just yank off all the wires because you will have mistakes putting them back where they belong. The method is to first create a "map" by printing a color picture of the board from your camera to serve as the restore wire locations. Second, make about two dozen masking tape labels marked numerically, and tag each wire you remove at the same time you mark the color map with that wire location so you have for example wire 7 and PCB location 7 matched.
When the swap is completed, the power can be turned back on and SunPump will start up again and run. Return the faulty PCB to SunPump by postal mail, so we can keep the replacement under Warranty.