Light wiring/LED help?!

If you're getting at least 12v at the kick panel connection, I'd unwrap the wiring in the rear where the taillight wires join the license plate wire and test again there. Inspect the harness from cargo damage too. If there's broken conductors and only a couple still intact, that could be the problem. As mentioned make sure you have good grounds on all the sockets. Just adding a jumper wire as an extra ground is the simplest way to check for bad grounds.