Charmglow tabletop heater: how do I remove the dome?

First make sure you have propane. Low propane can cause this too. Presuming its not the easy fix, its probably spiders that have built a web in the venturi (air) tube.

Remove the screws attaching the screen/shield to the body and it can be lifted from the body without taking off the aluminum heat dispersing shield. Next remove the 4 screws holding the burner in place and you should be able to lift out the unit to clean of of the spider webs. High pressure water may or may not work. You may need to use something like a pipe cleaner.