Rheem rr410T no hot water

SOURCE: Rheem 50 Gal Hot Water Heater will not stay lit

On the back of the gas valve (where you turn the temp up) there is a stem that actually goes into the tank that senses the temprature of the water it could be dirty or buried in sediment depending on how old the tank is, or just bad. if the tank is over 10 years old i wouldn't bother replacing the gas valve, the tank is probably not far behind. A new valve will run around $100.00 maybe a little less. You wont find it at menards or home depot in stock but they may be able to order it for you. Menards sells rheem products or try you local plumbing supply house. REMEMBER TO RELIEVE THE PRESSURE ON THE TANK BEFORE YOU WORK ON IT. IF YOU CHANGE THE VALVE DRAIN IT FIRST!

SOURCE: Rheem Hot Water Cylider Thermostat keeps tripping

Sounds like you have a faulty thermostat.  This is the unit that detects the water temperature, and if it is not where it is set, will kick the switch to allow electricity to flow to the elements you replaced. The thermostats are relatively cheap and if you have the knowledge to change the elements, changing these thermostats should not be a problem.

SOURCE: No hot water, Rheem Model RR612T, Electric Hot Water Heater, 60 g

If you don't have current, 0v from terminal to terminal, then you don't have voltage to the elements. Replace the thermostat but check that you have 220v to the thermostat. It is possible that your breakers to the unit are either bad or tripped.

SOURCE: I have a Rheem EcoSense hot water heater and all

Have you try to reset the power to the heater?Then turn the hot water facuet on to see if it will start up.

SOURCE: My Rheem hot water heater stopped putting out hot

If you are not familiar with the element, I would get someone that is familiar with one and have them do it. It's not something I would recommend you do based on your question. There's electrical, pressurized water tank, and a whole lot of water that may cause you to have a worse bad day.