There's a 99% chance that the wire got damaged underground after the first light. I would start by pulling up the wire between the first and second light and inspect it, I'm sure there's a problem in that stretch of wire. When you find the problem there's 2 ways to deal with it. 1.) replace the wire from the transformer all the way to the last light 2.) splice the wire together at the break.
I would recommend all new wire, to avoid future problems. A splice will be prone to corrosion no matter how well you attempt to seal it. Please keep in mind that a splice can only be done with low-voltage wiring.
Also, while you're at it, consider running the wire through inexpensive plastic pipe to help protect it a little better. |