HP Notebook 14-an010nr Will Not Boot From USB

[MaxProAndU]

We have a HP Notebook - 14-an010nr (ENERGY STAR) Laptop that refuses to boot from a USB.

Secure Boot has been disabled and Legacy Support has been enabled.  If you repeatedly tap ESC on startup, you can select F9 and see the USB drive in both UEFI and legacy options as-well-as a Boot From EFI File option. Regardless of the selection, it just goes to a blank screen.

We have tried three different USB flash drives, with the following  USB tools:

HP Cloud Recovery

Windows Media Creation Tool 21H1

Linux Mint

It sees a can read each of these drives in the Boot Manager, but gives nothing but a blank screen when selected. 

[WAWood]

@MaxProAndU 

If you're trying to reinstall Windows, changing to Legacy boot is a really BAD idea -- because HP laptops come with Windoes 10 preloaded in UEFI mode and that is what you need to use to reinstall Windows.

If you're trying to install a Linux distro, we can't help in that because we don't provide support for Linux.

[MaxProAndU]

Unfortunately, you've COMPLETELY missed the point/problem with this 14-an010nr.

The eMMC, which tests fine according to the built in test parameters (as does the memory) had a corrupt copy of Windows giving the 3FO code at boot up. We attempted to boot the HP Cloud Recovery for this machine from three different USB flash drives with no success. Secure Boot has been disabled. We tried booting with Legacy Support simply because almost EVERY HP online guide says to.

Just to make sure that the problem wasn't with HP Cloud Recovery (which has never failed us so far), we moved to a known good  USB copy of Windows Media Creation Tool 21H1: nothing. Tried 21H1 on two different USB flash drives: nothing. That's when we tried Linux Mint that's on a drive that has NEVER failed to boot: nothing. All you get each time is a blank backlit screen.

Right now, it is in UEFI Boot with Legacy Support & Secure Boot Disabled. If you enter F9 at startup, it clearly sees whichever USB flash drive we're using (HP Cloud Recovery/Windows Media Creation Tool 21H1/Linux Mint). It even offers "Boot From EFI File" and will let you search the drive and easily finds the bootmgr.efi file. 

Simply, it refuses to boot from a flash drive. What is it we're missing?

[MaxProAndU]

After extensive testing, we found it the be a bad power rail/circuit of the mother board.

Apparently, the UEFI runs so independently in this design, it can't see that the CPU isn't operational. It'll test the memory (or lack there of) and eMMC/SSD/hard drive, but as long as the UEFI is sensing power power it ignores it complete status of the CPU.

In a nutshell, the subsystem could see and read the SATA, USB 2.0, USB 3.0 and SD too the point of a file search, but only launched to a blank screen. The 3FO code at boot up was throwing us, being a too common HP problem. Turns out this code is derived from the faulty UEFI when it doesn't see CPU activity. We ended up replacing the eMMC with a SSD containing the drive image of working 14-an0XX, and received the same 3FO, with the SSD working flawlessly in the now "upgraded" donor.

After seeking out the schematic for the 858047 motherboard, we found the issue soon after. Sadly, with a replacement used motherboard with shipping being less than $40, we felt it was no long worth the additional time spent.

Moral: 3FO + blank screen on USB boot = bad motherboard.

[JorgeTR]

I would like you to guide me or give your opinion on my problem and know if it is similar to yours; also if you think I can repair it or better take it to an HP service center.  I did a recovery on my HP 14-an006la from the Windows 10 64-bit system, made the relevant updates, finished and started fine, turned it off and the next day it doesn't boot and only the backlit screen appears. I can go into the settings and even do a BIOS recovery but on boot, in both cases, it just shows me the backlit screen with nothing.  I have another HP 14 of the same model and I have already tested the hard drive, and if it boots, the memory also works perfectly; the keyboard does not lock as the shift key turns on and off its LED when pressed, the hard drive also works. I put an external monitor and nothing is seen, look for various solutions like pressing windows key + V, Windows + B, and if you restart the settings and / or recover the BIOS but still do not boot. Also press and hold for 30 seconds. the power button, remove the internal battery (motherboard) and the external one and nothing. The same thing is to try to boot from a usb with Windows 7, 8, 10 and still does not boot. AS AN IMPORTANT DETAIL, COMMENT THAT by pressing the ESC key you can enter the start menu and select: display F1 system information, or choose the F9 bootable media or enter the F10 configuration, but NOT the F2 diagnostic or recover the F11 system, as the screen lights up in backlight and shows nothing. Only if I disconnect the hard drive, it shows me the 3F0 error and already allows me to make diagnoses; display F1 system information, or choose the F9 bootable media or enter the F10 configuration, but NOT the F2 diagnostics or recover the F11 system, as the screen becomes backlit and shows nothing. Only if I disconnect the hard drive, it shows me the 3F0 error and already allows me to make diagnoses. display F1 system information, or choose the F9 bootable media or enter the F10 configuration, but NOT the F2 diagnostics or recover the F11 system, as the screen becomes backlit and shows nothing.  Only if I disconnect the hard drive, it shows me the 3F0 error and already allows me to make diagnoses.
P. D. Sorry for putting my question with the answer button, but your comment is the closest thing to what happens to me and it seems that you have found the solution; at least I understood you.