Trying to resuscitate bricked Spark Core v1.0

In the misty dawn of time, I purchased two Spark Cores. One of them has been functioning well for years, I dust it off occasionally to mess with the hardware stuffs. I’m a small electronics hobbyist with a lot more experience coding than soldering, if you catch my drift.

Anyway, my 2nd Core bricked pretty early on in its life, and recently I’ve taken up the task of reviving it. Documentation has been sparse on the ground, but I’ve got a programmer shield for it, and an ST link gadget and software. Should be pretty straightforward, one would think, but following the prevailing guide about the topic has my stymied.

I’m following directions posted here: https://github.com/particle-iot-archived/bootloader

Notably, I cannot unlock the bootloader (since I have the dim D7 problem, so I can’t seem to put the device in DFU mode by pressing the switches). So I proceeded directly to flashing. But no matter what I do, I get this error and cannot proceed. https://imgur.com/nAgC4fY

I would love to get this Core working again, I’ve had a lot of fun with my one and it’d be nice to have a 2nd so I don’t feel like I’m losing it if I embed one in a longer-term project.

Sorry if I’m posting this in the wrong place, Troubleshooting seemed like more the right home but I’m not allowed to create topics there.

In the intervening couple days, I’ve read everything I can find here on bricked cores. I can’t find anyone who seems to suffer from the “unable to connect to target” error that I encounter on literally any attempt to do anything to the Core in the Programmer Shield.

Help me @rickkas7, you’re my only hope! Is he still around?

On a serious note, I think this Core is just dead. I flashed an OTA firmware (probably something stupid, like flashing D7, or reading a LM34, or something simple), the RGB LED did its thing for a bit, then dim D7, and I haven’t been able to coax anything else out of it since then.