Have not used LOS before, so I played with it now.
It seems that cone of view must be positioned in front of the object, which is to the right, so you will have rotate object by 180 to make it look left.
(for all objects default angle 0 is to the left, so they should be drawn facing left, and then mirrored, which LOS takes into account, it seems)
Also another limitation seems to be that entire object must be inside cone of view.
So my advice would be to set Cone of View larger then needed and then set another condition which will compare player angle to eye angle. (you can put 360 if you do not have many such instances which will eat your hardware)
In example in the picture, cone of view is set to 360, and then another condition (last in line 6) limits it to 30 degrees behind enemy.
Also one more problem in your example is that you have 2 Enemies, and you text field will be overwritten by enemy who cannot see you, so it is enough that only one enemy cannot see you it will say "Player is Undetected"
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