"boot image did not authenticate" appears to be a secure boot issue, In your case it's likely a corrupted boot loader. Do you know what key to press on boot up to do the factory recovery? I think I would try that at this point. If you haven't already.
After getting to my BIOS and turning off secure boot, and activating legacy, I get more than an infinite black screen. Now it says to insert boot disk. So there's that.