Guild Wars 2

I can’t use this skill, cant click etc. I have unlocked all weapon skills btw.

This issue has come up before to where some players who have had warhorn #5 unlocked for a long time suddenly found it to no longer be unlocked due to some obscure bug.

To fix:
Enter a zone appropriate for your character level (a zone where you are not down-leveled) and kill 1-5 enemies of your level (usually 1 is sufficient). This kill will award the necessary experience to re-unlock the skill.