Long delay before starting to boot OS

[alistairlow]

TL;DR laptop screen stays blank for 60+ seconds after switching on, *before* the OS starts booting

Details:

• The laptop is an HP 14-an009na - this seems to be part of the same family as the HP 245 G5 (same motherboard, CPU etc.)
• The laptop was fixed at some point for water damage, but I don't know what was fixed or replaced
• I replaced the original hard disk with an SSD a few months ago - complete Windows 10 reinstall and updated all drivers, firmware and BIOS - I believe that the issues below didn't start until I did this, but I'm not 100% sure
• When the laptop is powered on, the display backlight comes on but the screen stays black for 60+ seconds before the HP logo is displayed, then Windows boots in around 5 seconds to the login screen
• The same symptoms are present if I remove the SSD and use the original hard disk, or if I use another SSD with only ChromeOS Flex installed, or even when I press F10 to enter the BIOS setup screen. So, the issue seems to be at the BIOS/firmware level rather than the OS
• Another issue is that when the laptop goes to sleep (in any OS), it cannot be woken up again - pressing a key or the power button seems to do something as the fan spins, but the display does not come on, it stays black
• Apart from these issues, the laptop works normally and performance in Windows is fine

While investigating, I noticed that some information in the BIOS is corrupt - see screenshot:

I've checked the following things that I've seen on other threads about slow POST:

• USB devices plugged in - there aren't any
• Tried a different power adapter - no improvement
• Tried with the battery removed - no improvement
• BIOS recovery from a USB memory stick - no improvement
• Ran a complete system diagnostics test - no problems found

However, I also noticed the following fix mentioned on https://support.hp.com/ie-en/drivers/selfservice/swdetails/hp-14-notebook-pc-series/10862293/model/1...: "Fixed hang issue caused by not being able to handle Feature Byte longer than 80 characters". Since I have a Feature Byte string that's longer than 80 characters, this seems like it could be the cause of the problems.

I've looked into how to how to write the correct information into the Born on Date, System Board CT Number, Build ID and Feature Byte fields of the BIOS, but that looks like it requires an HP technician.

Any suggestions on how to resolve this? The laptop is out of warranty by a few years, but I'd be happy to pay for this.

[alistairlow]

Further investigation reveals that I can boot immediately if I hit Enter while the screen is blank. The BIOS system log shows several lines with error code 000A, which I believe corresponds to "Product information not valid", so I assume that the screen should be displaying that error on startup (but doesn't, I just get a blank screen instead) and prompting me to press Enter to boot, hence the 60-second delay until it goes ahead and boots anyway.

To fix the "Product information not valid" error it looks like I would need a file to unlock Manufacturing Programming Mode to write the product information, but HP doesn't send those files out and the advice is to send the laptop to a service centre. However, it looks like there is no service centre in Great Britain. What should I do?

My attempts to fix this myself are complicated by another issue: if I try to boot the laptop in either UEFI mode with Secure Boot disabled, or legacy boot mode, I just get a blank screen i.e. I cannot enter the BIOS with F10, or the boot menu with F9. Can anyone suggest a solution  please?