In the fields, theres the building that needs a keycard to enter. When I was playing on master difficulty, turning the power box on the back off did not get the attention of the NPCs inside. I think this is a bug
This fuse box is meant to distract the guy that stands in front of the building on usual duifficulty.
But on Master difficulty he’s absent for some reason and there is nobody to distract instead.
Nobody inside the building shouldn’t go out, so there is no bug in this.
So you need to find another way (or a keycard) to get inside the building.
This is Master difficulty after all
Interestingly on normal difficulty the fuse is luring also one guy inside when the other has been taken care of already.