Rear lights for "Pontiac" wording

Hello all,
My question involves the rear lights for the word "Pontiac". They do not work for both my 1987 and 1988 GTs. The bulbs are fine. Anyone know what the possible problem might be?

Also, does anyone know if all of those lights will go off if only one light is bad?

I'm thinking a bad ground or other wiring problem.

Thanks for your help.
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