Okay, let's do one last thing. I'm running out of ideas.
Start the macOS Yosemite recovery disk, go into the "Utilities" menu and choose "Terminal". Do not
run Disk Utility
. Please provide pictures of those, to see what we have found
Once you are in the terminal, run the following commands (type and press Enter
This one will list all the hard drives your computer has. It should result in a similar output to this (note, I had to run a command more aligned with my computer which has an NVMe Drive):
This one will list all volumes, with no filtering, that your system has found.
The output will be similar to this: