First brief background. 2 SSD system, one with Windows, the 2nd with Ubuntu Linux.
I had to do a complete BIOS reset recently when replacing my CPU water cooler.
In Asus UEFI settings under Boot manager I at first can see my 2nd 1TB SSD with Linux installed so I do what I always do. Simply move to the top of the list, exit and restart.
But my machine refuses to recognize it and always boots into windows.
I also notice that the drive no longer has '[UEFI]' as part of its name.

According to my detailed notes I made when setting up my 'dual-boot' system these are the BIOS-UEFI settings that seemed to work
1-Disabled Fast Boot
2-Set CSM to UEFI only
3-Disabled Secure Boot
I made these changes and no difference except now my 2nd Linux drive doesn't even show up in my Boot manager list of drives!
Before my water cooler fix and resetting the BIOS I had no issues and my Linux install was working perfectly.
Anyone able to tell me what is happening? What should I attempt next?

eco_bach,

This should assist you:
http://linuxbsdos.com/2015/10/31/how...o-hard-drives/

Thanks. Yes I COULD reinstall again from scratch, but what would cause my UEFI bootloader to disappear from my linux drive? As mentioned, it definitely was being recognized before.

When I was still dualbooting Windows with linux on my Asus G751 I sometimes had issues with it booting to Windows regardless of selected boot medium after Windows updated. You might try removing the Windows ssd to try and force it to boot linux and if all goes well, reinsert the Windows ssd and try booting again.

"now my 2nd Linux drive doesn't even show up in my Boot manager list of drives!"

Is it possible that you bumped a cable or connector and now is not seen by computer?

I'd triple check that and then boot off a live media to see what disk programs might offer or hardware programs might offer.

Hey eco_bach ...

This happened to me on my Surface Pro 3 after a Windows 10 update, only difference being that I have a single SSD. I had to use the Windows bcdedit utility (in an Administrator command prompt) to restore proper functionality. The command in my specific situation was this:

c:\bcdedit /set {bootmgr} path \EFI\refind\PreLoader.efi

... you would have to change the portion after the path option to the appropriate entry for your own ESP (EFI System Partition) and boot loader.

If you don't know what this path is for your system, you can use the free Windows utility EasyUEFI to find this information and in some cases, actually correct it.

Cheers - It can be done ! :-)

Did this problem start after resetting your BIOS? If so, there's a clue there.