Help Survival Shooter

Hello everyone

I'm new at the Unity Comunity and I'm learning how to use Unity. I started with the tutorial, the first two were fine, but the third, the Survival Shooter was a little more difficult to me.
There are two issues:

The first one is when I build the proyect, because within Unity I test the game and it works fine, but when I build it to a Web Player, as soon as I start it, it pops up the same error a lot of times. The error line is:

"SetDestination" can only be called on an active agent that has been placed on a NavMesh

After that, the enemies spawn but they do not move, the score text does not show and neither the game over text or the animation of the screen fader. However this error does not occur when I test in Unity, as I said before, and all the things I mentioned, work fine

The Second Issue is the material of the line renderer of the shotgun of the player, it look black almost the whole time. These are the properties of the component, if they help in someway



I would apreciate your help