Convalescence Skill Gem has no activation button in the square-shaped skill UI

I am reporting a UI issue with the Convalescence skill gem. The problem is that there is no button to activate or assign the skill in the square-shaped skill selection menu.

The gem is socketed and meets all conditions:

Spirit is available (30/30).

Energy Shield is not full.

However, unlike typical skills that appear as square buttons ready to be assigned to an action bar, the Convalescence gem does not appear as a selectable option in the skill selection menu at all. The UI does not provide any way to drag, assign, or activate this "aura-style" skill. The only information available is the error message [Skill] can’t be used! on the gem itself, but the fundamental problem is the complete lack of an interface element to use it.

The core issue is not about meeting conditions, but about the missing UI button required to control the skill.