This is a weird one and it's intermittent during multiplayer, but constant when I try the practice modes.
The 3D elements are completely black. I can navigate the world by looking at the interface, which shows where objectives and enemy players are.
I can even fight by watching what the interface shows about an enemy's guard. But I cannot see the enemy, the world or any other 3D object.
This is the same in practice mode. Every 3D element is black so visual navigation is impossible.