My lighting lance does not work

i have been playing lighting lance for the last couple of day and now all of a suden it does not work. i have a 4 slot lvl 19 lighting lance and it does not let me equip it and when i put a new 19 it works for about 2 min than eventuly it does not work. when i add a socket to it, it also breaks the skill. idk what happing. ive been trying a whole bunch of difrent stuff to make my build work but it has not been working. please help me uggg