Any Idea Who I Can Call For Gas Fireplace Issue

I have a Superior Propane Gas Fireplace which is not working properly. The pilot light is lit; however, when I turn the wall switch on, the fireplace will not light up. The pilot light is still lit. BUT, when i take the glass cover off, the fireplace lights up and stays lit. If I return the glass cover, the fireplace stays lit and works fine. But if I turn it back off and try to turn it back on, same issue with pilot on but fireplace will not light up unless I take the glass cover off. Any idea on who I can all in the Knoxville or surrounding area to get this looked at?