That's not uncommon after a BIOS update, because the new BIOS version will be set to the so-called UEFI mode. If the old BIOS version was set to CSM/Legacy mode before, then it will not boot at first, instead it will load the BIOS and you will get the BOOT LED, but this can be solved.
With the BIOS in the modern, more advanced and nowadays preferred UEFI mode, it requires the boot drive to have a so-called GPT. But as your old BIOS was in the older CSM mode, it will have prepared the boot drive to have a so-called MBR when installing Windows. So you have to do a quick MBR to GPT conversion
for the Windows boot drive, then the BIOS in UEFI mode can boot from it again. It takes just a couple minutes to get this going again.
You might be thinking, but how about just setting it back to CSM mode? Well, Windows 11 will require the BIOS to be in UEFI mode. And Windows 10 support ends in 2025, then we will all have to upgrade to Windows 11. So by doing the conversion from MBR to GPT now, the BIOS can stay in UEFI mode and you would be ready for Windows 11. If you set the BIOS to CSM mode for a quick fix, you'll only have problems later.
A modern BIOS can be in two modes: Legacy/CSM (Compatibility Support Module) and the newer UEFI (Unified Extensible Firmware Interface) mode. Since all BIOSes are UEFI BIOSes nowadays, naturally they work best when set to UEFI mode. But also, every modern BIOS can be set CSM/Legacy mode, in order to behave like an old BIOS from many years ago. This is so it can work with older operating systems which have no or only limited support for UEFI, such as Windows 7. The problem lies in the fact that switching between those two BIOS modes after
you have installed Windows will make the boot process fail.
When Windows detects a CSM/Legacy BIOS during installation (for example on an old board or an old BIOS), it prepares the boot drive to have an MBR (Master Boot Record).
When it detects a UEFI BIOS during installation, it will prepare the boot drive with a GPT (GUID partition table) instead of an MBR. The BIOS set to either mode (CSM vs. UEFI) will only boot from a drive that was prepared accordingly for that mode (CSM needs MBR, UEFI needs GPT). That's why you need to do the conversion for your boot drive once your BIOS is set to UEFI mode.