The skill gem cannot be used

My level 19 'Shockwave Totem' skill gem with +20% quality can't be used after being placed in the skill slot. I've tried various methods, but it still doesn't work. I need your help.[https://i1.hdslb.com/bfs/new_dyn/c195638b7c109f4de743a9525efbe33b11213338.png@1192w.avif]