Epoxy

[justplugit]

More than a few things it could be:
Did ya measure the 2 parts exactly like the label.
Did ya mix it twice as long as they tell ya.
Did you use metalic paint as that can be a problem.
Did you apply it and exhale on it or run it over a propane flame to break the bubbles.
Did you apply it and dry in a humid free enviornment.Humid weather has been a bummer.

Those are the things you could
look at first.

Hope it helps.

[Christian]

also, oil from your hands, on the plug. wipe with alcohol before epoxy, or dont touch the thing at all.