Where would you guys start troubleshooting a no-power issue with an amp?

The main power lead goes directly to the battery via a fuse. The ground is short and terminates near the amp. Jumping the remote lead to the main power causes the amp's light to turn on briefly, then go out. The main fuse appears to be good.

This has been working for a year when it stopped out of nowhere. I've tried two amps and they both have similar problems.

 

Turns out that ground point no longer works. How or why, I have no clue. It's worked for the last year and looks like a good ground. I moved the ground point and it works fine now.