Cannot Execute At This Time

I've been getting this same damn error every time I try to attack a non-moving enemy/object during a quest (i.e. a tree, rock, etc.). As a puglist, I use "Bootshine", but it says "Cannot Execute At This Time". Sometimes I have managed to repeatedly button-mash and click and it somehow, sometimes works. Otherwise, I have to wait for someone else to attack it and then immediately afterwards, I'm allowed to attack. I've used this "technique" before, but I don't want to have to keep doing this.