Rheem (GE) 50Gallon Water Heater Failure
Rheem water heaters sold at Home Depot and other big box stores under the "GE' brand routinely fail due to inadequate sized vent openings located at the bottom of each unit. The small size of the openings allow lint to collect causing the unit to overheat and a fuseable link to melt causing the unit to shut down. The unit is a sealed item. If you open it to repair the link you violate the warranty.
Rheem will send a new part which takes about four days which means your client will be without hot water for that period of time. After their service person installs the new link and it fails again then and only then will they honor their warranty and provide a new unit. Seems like a lot of effort when the whole issue could be avoided by simply purchasing a different brand water heater.