Atwood 8835 - iv will not ignite - 9 year old furnace

I don't know about the light. But, most furnace problems are because Wasps (or Mud Dauber Wasps ) have built a nest, or nest's, in the furnace outside vents.

If it can't get fresh air or get rid of the exhaust gases it will not light.

Use a flashlight to look down the intake and exhaust tubes and see if there is anything in there.

Even if you can't see it this could still be the problem. I once removed a furnace, shook it upside down, and dumped a whole coffee can full of wasps nest's out of the plenum.