Can’t Co-Op Ascendancy trials

So I’ve been grinding a few characters up enough to start ascending them with my gf, but every time she and I are in the room to put Balabala’s relic into the altar it just always flicks out of my inventory and flops on the floor.

I’ve done everything to try to get it to work

Tapped Z, held Alt, reloaded the area, reloaded the game, even started a new character, but always the same thing the relic flops down on the floor rather than working properly.

I can solo place the relic in the ascendancy altar but what am I done wrong here?!?