Gas valve operating would indicate that there is power to the circuit board.
Have helper turn on water heater while you are at the unit. Listen for ignitor to spark.
You could have a helper turn on water heater while you use a long lighter to ignite gas inside burner area. Becareful as it could flash back!
Check the ignitor for proper spacing. Disconnect the ignitor wire, test it for conituity.
Check the porcelain on the ignitor for cracks.
Call Suburban for local repair person or shop. It could be bad circuit board. Could be still under warranty!
