Electron Debugging Not Resetting Automatically

Not sure if this is a hardware or firmware question, but:

Just yesterday, I was successfully debugging my Particle Electron via Eclipse and a ST-LINK/V2. Unfortunately, something happened, and I needed to re-checkout the firmware from the Git repository (instructions here: https://docs.particle.io/faq/particle-tools/local-build/core/#check-out-the-source). I’m using 0.7.0-rc.1 because there were compiler errors in release/latest (https://github.com/spark/firmware/pull/1340).

Anyway, all other things being equal, when I go to debug my board, Eclipse pops over to the debug perspective, but instead of halting on main, it gives me this:

“Break at address “0x0” with no debug information available, or outside of program code.” Here’s a screen shot.

It took me half a day to notice that the board wasn’t getting reset after the binary was loaded onto the device. If I hit the reset button on the device, and then hit the play button in Eclipse, it will halt at my breakpoints that have been set up and run as expected.

So my question is, what did I forget? Is there something that I’m missing that restarts the board and halts at main (instead of 0x00) like it’s supposed to?

I realize its now working, but different behavior from one day to the other is always a scary thing, and I’d like to know what’s going on.