Suburban water heater wont relight after first start

It could be same issue as Smokeskull.
I do not believe Suburban is having any more issues then the rest of the products using circuit boards.
Make sure all connections are tight.
I would also look at the gas valve ground connection.

Is Suburban having an issue with bad circuit boards? Just had to have mine replaced only 1 year old. Gas side kept going into reset after lighting off and running for 10-15 minutes or so, then remained in reset condition. Like you I had to turn off the switch and back on again, would light off and get to temp, kick into reset again.

I took the t-stat out and realize it was installed crooked and not seating properly on the tank. I cleaned the surface and install correctly and it works perfectly now. Imagine its been like that since new. It would have drove me crazy. Camper is a 2004 Lance.

Ya i am thinking the t-stat might be wonky too. Last year when i used the camper water would drip out of the releif valve but its not doing it this year. I will report back thanks again.

It could be the ECO or thermostat not closing.
Fairly easy to replace and available at most RV parts store. Not that expensive.
Example of what they look like. Verify your part number.
ECO/thermostat

I let the tank cool down and had the wife run some hot water. I stood by the heater and it made no noises. Finally the fault light came on. I had her cycle the switch off and on and it lit up immediately. I guess in a way its a built in gas saver. Its easy enough just to cycle the switch once in a while begoe you need hot water.

I had a similar problem on a Dometic Water Heater. 3 trips to the dealer could not solve the problem. I would say this was about a 90% cure. Remove both thermostatic switches. Clean the face of the switches with a Scotch Bright pad as well as the face of the tank where they touch the tank. It you want to get fancy, apply a bit of thermal heat compound they use CPU cooler (NOT the adhesive type !)

For some reason the gas valve were just not opening up !

Appears to be a DSI water heater.Manual

I would start by cleaning the ignitor/flame sensor.
Make sure they are adjusted properly.
Switch should be left in the "on" position.
Make sure the ground connection for the gas valve is clean and tight.
It is possible that the unit is shuting down by the ECO opening rather then the thermostat.
Does the red light adjacent to the switch come on?

SW6-D is the model number

Post exact model number of the water heater