Pinebook Pro refuses to boot from eMMC

[pivic]

Good point.  Do remove the eMMC.

If you've never done this, it isn't obvious, but you just pull it straight up to remove it.

I should mention something else that isn't obvious: all the boot code (including U-boot) exists on the boot device. 

If you have boot code on the SPI F-ROM, that runs at startup.
Else, if you have boot code on the eMMC, and it's enabled, that runs at startup.
Else if you have boot code on the micro SD card, that runs.

So unless there's something on the SPI F-ROM (very unlikely), as long as the eMMC can run, a corrupt U-Boot on there will prevent you booting any other way.

Thanks, both to yourself and to @wdt. I've fully charged the computer via USB-C - i.e. until the red light went out - and then removed eMMC.

After that, I've attempted to boot from all of my four different MicroSD cards again, still without any flicker of light from the LEDs on the computer. Before my issue, lights went on when I held the power button for about a second. Now, nothing happens. I've yet again checked all cables but can find nothing that's disconnected or any kind of soldering that seems to be broken.

I also attempted to attach eMMC back and tried the hardware switches in combination. The computer battery is charged, but nothing happens when I try to turn it on, regardless of MicroSD card or image (that's previously worked to boot from).

At this point, I wish there were somewhere I could send the computer for repairs. I don't want to get blindsided by any old repairs page. If you happen to know one online or, preferably, one in Sweden (where I live), I'd very much appreciate a word about it.

Once again, thank you all so much for helping me. I'm happy for all the help, kindness, and wisdom that you've all imparted on me, and if I could thank you all in the flesh, I would.

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Does the green power light go on at all?  I believe it's controlled directly by the pmic so it should turn green even if the CPU doesn't boot if there is enough power from the battery.

Thanks, but it won't go on; No lights go on whatsoever, apart from the red battery light when I'm charging it (except for when it's fully charged, at which point the light goes out).