The error is pretty clear. The installer main image cannot be found.
It would be helpful to know what your configuration looks like. Looking at that page, it’s hard to guess what yours may look like. So the only guesses (until you provide your config, where your files are at, and so on) would be a misconfiguration on where inst.repo is pointing to or the data that it has. It would also be helpful to know more than just that error, such as what the on screen logs look like.
With that said, perhaps taking a look at my guide may be helpful for you. In particular, the adding distributions section. Granted, I use grub2, but the mirroring of the DVD download and boot options such as inst.repo and inst.stage2 still apply.
but it’s looking for a file that doesn’t exist (or is in the wrong place)…
because when I go to the path it indicates in the error I can’t find what it’s looking for (…/LiveOS/squashfs.img for example)