I have windows 10 preinstalled on mine laptop. I love both ubuntu and windows so I planned to make DUAL boot my laptop. Then I have installed Ubuntu as 2nd OS to my LP. Everything was successful and I had configured the GRUB(Basics like time out and Default). Then I have to restart my computer and GRUB menu appears and I choose to use Ubuntu.
After my work finished in Ubuntu, I wished to use Windows so I had restart my laptop and GRUB menu appears and chose Window. Suddenly I realized that I forgot some file to bring to Windows so that I wanted to go back to Ubuntu so again restated Laptop. After the restart, I came to know that there is no GRUB menu so that I tried to load using BIOS but I did not found Ubuntu there also.
Both the OS has booted using UEFI(Secure boot off).
I have checked that the Ubuntu folder is there is the EFI folder(Checked through windows command prompt).
Also made the GRUB as default
I have Ubuntu partition also.