Hello Forum,
Wanted to post this here in case someone else is confused why their enemy tanks are not moving despite seemingly being on the NavMesh. If that is the case I suggest you take a close look at your tank with the navigation preview on.
As you can see, the NavMesh will consider your tank as part of the landscape and exclude it thusly. Move your tank upwards until the NavMesh fills in beneath it and assuming your code is in working order, your enemy tanks should begin to move.
I hope this helps someone out there.
Cheers.