I have used this board a lot of time with an Intel Raid Controller, i never had any problem like this.
First thing to do is:
Check if the controller card that you are using is on the THOL
If no, this could be reason. I remember, with a particular card, i could not boot on to USB when the non-tested external card was connected on the machine. Weirdo!
If yes, then follow to the next steps.
Let me explain to you how to update the bios of the board:
CMOS clear using the jumper.
Firstly, you go on to the download page of the board.
Download this onto your desktop:
Extract the zip files.
Copy all the extracted contents in the folder to a FAT-FORMATTED USB (root directory of the usb)
Insert the USB to the target machine.
Boot the system into the BIOS (F2)
Go to Boot Manager
Select the EFI Shell and press Enter
It will automatically boot onto the EFI shell.
Once on the EFI shell, the shell will look for the file startup.nsh automatically in the USB.
If it does not find the startup file, try another USB.
It will load the firmware package automatically and you just need to follow the instructions.
Note that: sometimes with a controller card, after configuring the raid in the raid bios, the boot options in the board bios is changed to defaults. You will need to set the boot options devices again. Save and Exit.
Dont forget to exit the EFI shell, type exit. :-)
Let me know how it goes.
All the best,