Just had a customer bring in a HP 14s-fq1010nm to do some maintenance.
After updating the BIOS to the latest (F.35) I get black screen (no backlight turning on). However the backlight turns on if I connect an external display to HDMI, but when booting to Windows, both displays remain black.
After disconnecting internal LCD, and plugging in external display via HDMI, it works on external.
I tried downgrading it using official method - using an USB drive with older BIOS version, but it fails, saying that the BIOS files are corrupted. I used about 5 different older BIOS versions...