Two spells name "proie marquée" in french on hunters says it it "already activated" and won't let me use it anymore.
I have an idea of what make that trouble happen.
I think i tried to use that spell using "shift" to use after and other kind of magic arrow. And after that it was not possible to use it anymore for both my hunter sagani and main char.
I have seen that many people have that kind of bug but maybe you could detect the origin of the bug more easier with my report.

Good luck and thanks for the game.

I also have this bug on my hunter. I think mine also triggered when trying to do a shift-sequence. Reloading/dismissing does not restore the ability.