Turn off the power on the Atwood Eco water heater. Remove the nuts securing the thermostat junction box cover to the back of the unit with a socket wrench.
Pull the junction box cover away from the water heater. Find the reset button near the heating element. The reset button is red and is probably protruding out if it requires resetting.
Push the reset button in with your finger until it clicks into place. The top of the button remains flush with the side of the water heater.
Place the junction box cover back onto the Atwood Eco and secure with the retaining nuts. Turn the water heater power back on.