does the socket look fairly clean, by that, I mean, no corrosion?
wet it down with some marine type electrical spray/electrical socket cleaner, might clean it up enough to make the connection...
as long as your "night time" lights work, your all set anyway, I guess..
my old ford.. only bulb I've had to ever replace, was the left rear brake/signal bulb and the cab mounted, center rear brake light...... at 110K, I wish I could say that for the rest of the truck
.. but no real complaints, considering the abuse it gets.
edit * did ya check fuse?
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