Chris, that's what Fantastic told me on the phone. Unfortunately, I'm afraid to go up on the roof. So I took the screen off from inside and was able to reach my hand up and did push that plunger many times. Also gave it a squirt of DeoxIT. Maybe I'll try some more. Might try to get a small tool up there to loosen the nut and jiggle the ground wire around, but not sure I can do all that through the fan blades.
Old-Biscuit....Auto mode works fine other than the fan doesn't run (yes, the speed knob is on), i.e. the vent cover goes up and down.
Dick B....I have a multi-meter, so thank you for that suggestion.
Thank you all for your suggestions!