Can't use frenzy gem skill with manaforged support

If I equiped frenzy linked with manaforged support on any slot, the attack slot gets greyed out. If I unequipped manaforged, the attack can be performed. Those two skills are shown as compatible.

I'm playing on PC using a controller, playing on ancestors league.

i am having the same issue

The whole point of manaforged support is, that you don't need to (and cannot!) use the skill manually. Frenzy gets triggered by the support automatically.