Teleporting boss that chases you/ HOW TO USE LINEOFSIGHT

So basically I have a sprite that pathfinds to you very slowly, but if the sprite nodes see you in there line of sight it teleports the monster to the sprite... how do I use lineofsight.... nothing is happening

Generally speaking line of sight works something like:

does A have line of sight to B?

THEN

required action e.g. spawn at A sprite C

So without further information about how you have your events I am a bit stuck about what to suggest…