So you have a 2D setup and you want a flying character to follow behind the player?
My first question is: Do you really need to use a nav mesh? It seems to me that in a 2D environment, using that kind of navigation might be overkill. But I don’t know if the follower will need to perform more complex movements to avoid obstacles or not. For example, in Ocarina of Time (and probably most other Zelda games), Navi floats around Link and can pass through walls without issue - it doesn’t perform any advanced nagivation.
My second question is: Is it important that the follower be independent of the player? Would it make a difference if the follower were simply “attached” to the player to make it look like it was following? If not, it would save a lot of headaches to simply attach it, maybe add some movements to make it look like it is not rigidly attached.
But if you do truly need to use a nav mesh, then what exactly is the issue? You should be using AI Perception instead of Pawn Sensing - I don’t think AI Perception was a “thing” back when this was originally posted in 2006. Although … do you really want this to only work on sight? I have no idea what the intent is here, but it seems like if you use pawn sensing there’s a good chance the follower could “lose” the player. But if you do want it to work this way and you have this set up but the AI will not work unless the character is “standing directly in front of it”, that seems to indicate that the parameters set for AI Perception for the Sight sense are not high enough to allow the AI to see the player. You can use the AI Perception debugging to show the senses … I think it might be Numpad 4?.. might be a different hotkey, try a couple. It will show the sight range of the AI.