GSW Series 5 water heater is electric water heater.
http://www.gsw-wh.com/index.php?context=/products/waterproducts/gsw/electric/standardThe link above goes to the GSW page, but
the manual does not match the product shown in photoGSW has a phone number in the manual:
1-888-479-8324
I cannot see the manual, but I might be able to help.
Every electric water heater has a red reset button located on the thermostat.
Normally on a two-element thermostat, the ECO or reset button is located behind the upper panel.
Your water heater seems to have a box located where upper panel is located.
Without the manual, I do not know what functions are performed by this box.
If there is a thermostat setting on the face of the box, then maybe there is also a red reset button.
That being said, you want to drain your water heater.
The GSW water heater has a drain valve.
If the valve is plastic, rotate the knob counterclockwise.
If the valve is brass, use a screwdriver to rotate stem counterclockwise
The photo shows the screwdriver slot for brass drain valve
If your water heater will not drain, it is probably clogged with sediment at the tank bottom.
http://waterheatertimer.org/Water-heater-will-not-drain.htmlConnect a washing machine hose to drain valve.
Connect garden hose to outdoor spigot, and to washing machine hose.
Turn on outdoor spigot for 10 seconds and this will open the clog.
Repeat procedure if clog is still there.
If your water heater is clogged with sediment, you will want to clean out the water heater:
Follow the step by step on link below:
http://waterheatertimer.org/How-to-clean-sediment-out-of-electric-water-heater.htmlIf I can assist you more, add a comment and I will respond