Error A127 means the elements mis-wired or the control board failed and the heater was disabled. The following steps can help you check the issue.
Disconnect power to the unit.
Check the wiring connection to the heating element.
Ensure both wires are properly connected at element and board.
Check the ohm reading on the heating element if wires are properly connected.
If acceptable ohm reading is present, replace the board. If not, replace the element.
Zwell is dedicated to getting homes closer to net zero through the installation of new energy-efficient hybrid water heaters. We are not currently equipped to do service or repair visits but we want to be as helpful as possible. Feel free to reach out to us here or for more information, you can contact the Rheem Hybrid Technical Services Department at 800-995-0982.