iATKOS | United Kingdom

I've reset these computers a LOT and installed OCLP on them successfully, and never before have I had this issue at this stage of the process.

I know this is technically more of a "getting your Mac ready for OCLP" but wondered if folks might have thoughts.

Basically, I have a good condition working 13" MacBook Pro (early 2011) and was installing High Sierra on it and running all the official updates to make sure to get any firmware updates.

It was in the process of installing the 2020-006 Security Update (I assume there are some firmware updates baked in there too) when it got stuck on the grey progress bar screen and had text saying "Rebooting" (which I've never seen before). I didn't touch it. But it eventually turned off and turned back on, only to show the "no" symbol (circle with line through it).

I can boot from a USB drive, but it does not detect ANY hard drive that's plugged into the SATA cable now. I've tried multiple hard drives and it still doesn't see them in Disk Utility via the USB drive.

I have never had this happen before—did the firmware update going wrong somehow brick the ability for the laptop to read the hard drive?? Any way to fix this?

EDIT: I tried reinstalling macOS High Sierra to an SSD connected via USB, but it won't let me, saying "the computer is missing a firmware partition."

EDIT 2: I booted from a separate HDD I had that had High Sierra on it. When I boot from that, it DOES detect the internal drive. So it's like it's just not detecting it at boot. Hmm.