Here is a procedure to trouble shoot the propane side of an Atwood heater.
The "switch" refers to the switch/indicator on the control panel. There is a connector between the control panel and the heater. Make sure it is not loose.

1. Clean the contacts on the cirucit board. If it still isn't working.

2. Pull the brown wire with the fusable link from the TSTAT connector.
Connect a volt meter between the wire and ground (If no volt meter DW's
tongue will work.) Press switch. If you read approx 12 volts the link is
good. If not either the connector between the switch and the heater is
loose or the fusable link is bad. If the fusible link is bad temporarily by pass it and replace when possible.

3. If link is good pull the second brown wire from the TSTAT and jumper both
wires. Press switch. If the heater works, replace the TSTAT (micro
bucks). BE CAREFULL If the heater works there will be flame.

4. If the heater does not work, pull and jumper the wires at the ECO switch.
Press switch. If heater works replace the ECO Switch. (micro bucks)

5. If heater still does not work, you probably have a bad circuit board.
(big bucks). If you can find a similar board replace yours and test
the heater.