This problem had me stumped for a good hour.
I initially tried to do the challenge by myself using the docs and got pretty close. I managed to get it appear at the first waypoint, then move to the second. But it would not move to the third, or update the index count. I tried a few different ways to go about it, but I kept getting the same issue or the enemy would not move at all.
I eventually just followed the video lecture and did exactly what he did. It still did not work. First time that happened, I thought unity or visual studio was broken.
Thank you, Thank you, Thank you for figuring out the z-axis hang up. I would have been stuck forever lol.