This generally occurs if you are using old kind of hard disk partitions and BIOS mode.

If this does not solve the problem, then go to Troubleshoot > Advanced Options.

Then click onStartup Repair.It will automatically repair the boot up problems.

Fix Bootmgr Is Missing Error Windows 10 1

Method #2 Use Commands

Another command prompt solution exists, if the above methods dont work.

For this you should use the same installation media and enter the Command Prompt window as mentioned above.

Then enter the following commands one-by-one.

Advanced Options Windows 10 Repair 1

you’re free to use the BCD Deployment tab on the software.

For single users its a free software.

You just need register for it.

Rebuild Bootloader Commands Windows 10 1

For companies and group of users, you may need to buy it.

Using the installation media, enter the command prompt and bang out the following command.

If the above command fails to work, you might use the commands mentioned in the screenshot below.

Update Mbr And Bootsector Windows 10 1

Write Mbr Windows 10 1

Repair System Image Windows 10 1