It seems that not all Proscenic robotic vacuums have no-go zone function, for example, 820S, 830T, 850T. To set no go zone, you have to use magnetic tape or boundary strip.

To protect the delicate accessories and furniture at home against the product’s accidental bumping, as well to prevent the appliance from moving into a restricted zone to avoid any property damage, we need magnetic tape to make no go zone by ourselves. 

Have you used it? And I find the tape can be cut to fit into practical use.