Enchanted weapons have a charge when you use them. Attacking a target takes some of the charge each time you hit them. Keening has been used so much that it is out of energy, so its special attack cant happen because there is no charge behind it.
Unfortunately once Keening's charge is gone thats it you can't recharge it like other enchanted weapons (without using mods or commands on a PC).
It lasted about 10 swings for me.
this dagger has a glitch it is supposed to last forever but it doesnt so u guys can blame bethesda for that it is supposed to be like the bloodskall blade (I belive im right) and never run out of its enchantment its just a bug in the game
i gave it to arniel. how do i get it now?
I don't accept that this blade is working as intended. I think that's the dumbest thing I've ever heard. The devs made a broken game, this is known. It's just another one of the many bugs skyrim has in it's code and if you can't see that, then you obviously haven't played the game enough. The mere concept that it was intended to function this way is purely asinine.
If you finish the quest he mentions that you didnt need wraithguard to wield it prompting him to think this one is a fake. Its broken because its not the real dagger from morrowind.