Can't equip darkmantle set in AMR, system wont allow it

cannot equip more then one darkmantle piece 0.5 leather dungeon tier, ARM won’t allow it.

I don’t quite understand the issue – could you provide a little more detail? Are you getting an error message when you try to equip an item? Which feature are you using: Best in Slot or Best in Bags?

Also, it helps us to help you if you press the “help” link next to the big Best in Bags or Best in Slot section header, then click Create Support Post, then copy the generated snapshot ID here. That allows us to see exactly what you see and resolve your issue more quickly.