I had a Raspberry Pi and Ubuntu Mate running on that. One day I decided to attach a hard drive with that and convert that into a NAS. I completed the setup and I was able to access the NAS from my windows machine.
However, next day when I switched Raspberry Pi on, GUI didn't come up. I showed some icons on the desktop and then converted into Green color.
I can't do anything with that now. I am clicking at places but unable to see any option. Pressing different keys also not making any difference.
Any idea whet went wrong and how to correct it?