Unit lights, runs about 10 seconds, then shuts off. Will light most every time but will not stay running

make sure wiring is correct especially if wired 120 volt read instructions inside panel

Try cleaning the flame sensor rod it will be in front of one of the burner tubes.

1) For tank-type gas water heaters:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

2) Re-post question on fixya or Tank forum and include information that shows on product label usually located on side of unit, so expert can determine which product, and what error codes and controller are revealing.
http://www.thetankatwaterheaterrescue.com/forums/forum3/

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

check the thermal coupling for the pilot light. if it goes out it will shut down gas supply, its a safety feature to put out pilot light if the thermal coupling is bad. to prevent gas from leaking and causeing a fire. check coupling.

i think your flame sensor is bad but you will need to confirm that with rheem i am unsure what the c7 is for but code 12 is flame failure and there could be carbon build up on the flame rod...

that is a flame failure check flame rod for carbon build up or qualified technician check it

if you have the exhaust run together it will not light up,, they have to be seperate,, the computer board sences the unburnt gasses and will not allow it to start,,

Try this first before condeming the unit.

1. Turn off the power supply to the Digistat SCR (receiver unit)
and leave for 5 seconds.
2. Turn on power to SCR unit and check red light is on.
3. Press override button No.2 and check the green light comes
on and boiler fires.
4. Press & hold down button No.1 (Keep depressed), then
press No.2 and keep depressed. {The Red LED light will flash
a couple of times and then it will go out}
5. Now release both the buttons – {the two LED lights should
come back on}
6. Get the Digistat+2RF/+3RF unit and stand two metres away
from the SCR unit with the Digistat+2RF/+3RF unit in your hand.
7. Remove the battery cover and fit the batteries.
8. The Red LED light on the SCR will now flash for approx. 7
seconds.
9. This confirms that the radio signal is being sent and
received.
10. The Digistat+2RF/+3RF and the SCR are now successfully
linked by a dedicated RF address.

have service completed