Use the Startup Disc Creator not the Rufus. Read why.

[kalpana]

Rufus sometimes screw up the Ubuntu grub installer. Don't use the installer on it.

Just use Startup Disc Creator after import the Ubuntu installer onto a USB stick. Get another stick and then download the ISO onto it. You will need 3 USB ports and 3 8GB (or higher will be fine.) USB sticks.

Go to Try Ubuntu out. Then go to Startup Disc Creator. Point at the ISO on one of the USB stick. Point at the empty USB stick at the bottom. Hit Make Startup Disc button.

This should fix the grub installing issue. So far tested three times. No failed.

i don't know what the Rufus is doing to the Ubuntu installer but I wouldn't recommend to anyone.