i will try.
you bought 8 of those 'tubes', and 3 don't work.
did those three ever work? these are designed to fit into a 4' shoplight fixture for t8/t12 bulbs. it appears they are self contained like cfl's, and you must bypass or remove the ballast and other circuitry for the floro's. if you do not, the ballast of the light fixture will fry the led stick.
if they did all work, and you have bypassed/removed circuitry from your fixtures, then i'd ask for a refund. they appear to be based in america, and 99% positive feedback.
where did you get the fixtures? did you remove or bypass the ballasts?