Where is the re-ignite switch on a RUUD achiever...

Question

It started getting cold so I checked the thermostat. We have an electronic one that shows the time, temp, etc. It was way colder than it was set for and I noticed it showed a flame under the desired temp we had set. I have no manual from the previous owner and the RUUD website is down :( I opened it, but cannot seem to find what to do...please help. Thank you!