GPT boot repair guide

Method 2. Use diskpart/

If you are a Windows 10 or 8 user and you prefer free methods to fix UEFI boot error, you may follow below solution to solve this issue now:

2.1 Use diskpart to repair Windows 10/8 UEFI

    Insert Windows 10/8.1/8 installation disk or installation USB into PC > Boot from the disk or USB;
    Click Repair your computer or hit F8 at the Install now screen;
    Click Troubleshoot > Advanced options > Command Prompt；
    Type below command and hit Enter each time:

diskpart
DISKPART>
sel disk 0
When the message "Disk 0 is now the selected disk" shows up, type:
list vol

    diskpart will now show the full list of volumes on your PC, find UEFI volume from the list: UEFI partition will be on Volume 2.
    Type below command and hit Enter each time:

sel vol 2
assign letter=G: Note: G shall be a unique drive letter which cannot be already used;

    When the message "DiskPart successfully assigned the drive letter or mount point", type below command and hit Enter each time:

exit
cd /d G:\EFI\Microsoft\Boot\
cd /d G:\Boot\ or cd /d G:\ESD\Windows\EFI\Microsoft\Boot\
Note: G is the drive letter you signed to UEFI partition and remember to replace G with UEFI’s partition letter.
bootrec /fixboot
ren BCD BCD.bak
bcdboot C:\Windows /l en-us /s x: /f ALL Note: c:\ is the drive where Windows 10/8.1/8 is installed on.

You can also run: bootrec /rebuildbcd > hit Enter;

    Type: exit in Command Prompt > Restart PC.

Now UEFI boot is fixed and Windows 10/8.1/8 can be boot again.