HP machine gives “Boot device not found” and hard drive 3F0 error after rebooting Ubuntu 18, can't boot from USB

Solution 1:

RE: USB boot, HPs are very finnicky with getting booted. Your disk needs to be in the right format and you have to get a boot menu to select the drive proper to boot too. I had this problem trying to boot Ubuntu on a stick, and ended up going old school with a DVD drive.

RE: The Hard Drive

If you're getting read/write problems, unfortunately you are hosed. The drive is already dying.

The best bet is to try to access the drive from a live env and try and recover what you can, then replace the hard drive in the system. Hard drives die for all sorts of reasons, and there's no way to really diagnose it or repair a dying drive.