Can't get GraphUpdateScene to work

I’m trying to get a simple door to work, but after trying various ways to do this I’ve decided to ask the experts.
I’ve tried to set the walkable tag to false with a GraphUpdateScene script after reading the docs and watching the youTube video, but I can’t get it to work.

My first question would be do these work on navMeshes made in another program?

I’m creating a empty object, adding the component and then creating a polygon to cover a few nodes. I’ve tried setting the walkable node and tried changing the tags, but every time my AI just ignores it and walks through the area I’m trying to block.

Any thoughts on what I could be missing? Your youTube video was great, I can’t see that I’ve missed anything, unless this doesn’t work on a navmesh?

I was able to set a node to un-walkable with the Edit Links button on the AStart Path script, but I couldn’t find a way to alter this through script to switch it back to walkable?

Any thoughts or suggestions are now welcome as I’m pulling my hair out. Basically I’m trying to lower a drawbridge after a event to allow the player to move onto a new area of the map. The player is using path finding because this is a action RPG type game in a similar style to Diablo.