why can i equip twin machine gun but can't use the Photon Arts (Bullet Hail, Assault Advance, Satellite Aim, Gunslinger Spin)? Hunter Subclass Fighter lvl 50. thx

You can only use PAs when you have either a main or subclass for that weapon. In this case, you would need to play gunner/fighter or gunner/hunter.

gunner/fighter is high damage, but very, very hard to play.

gunner/hunter is apparently easy.

I thought because I am able to equip the twin machine guns I'd be able to use PA too. Thanks for clarifying.