LED light bulbs not working when installed in slideout

Same here. with old incandescent lamps polarity don't matter
But with LED's Well some are wired to self correct for polarity errors (my favorite 20 buck a pop lamps do that) some (my favorate less than half that) do not and the techs who wire the fixtures for 1141's well. they don't always pay attention .. not to mention some lamps can be reversed as well.

I have some marker lights where it does not matter how you wire the socket but the wedge based lamp only goes in one way the other way it don't light.