I have two MS-01, one is running Windows 11 and the other is running Unraid. I could not get either of the computers to boot the 1.26 Bios update via USB (I had not yet seen the method mentioned by “kenosborn” -- see above). I then tried updating inside windows by running the AfuWinFlash.bat and it worked with no problems. Then back to the MS-01 running Unraid via the bootable USB drive, and as before it would not run, it would only go into the splash screen for the MS-01 UEFI. Setting the UEFI to use the USB did not work even though the USB showed as bootable.
I removed Unraid from that computer, loaded an early version of Windows 11 (2021, less security steps to avoid) and easily updated the MS-01 Bios – cleaned the windows off the computer and reloaded Unraid. I spent less time removing and reinstalling than the time it took trying to use the USB drive. So, if the USB doesn’t work for you the Windows method works great – no other steps than running the .bat file.
I would try the “kenosborn” method first, but if you still have problems...