Unable to unlock boot-loader

Hi,

My android tablet is iBall Brace-X1 which is….
• Android: 4.4.2
• Baseband version: iBallMOLY.WR8.W1315.MD.WG.MP.V34.P1,2014/09/28 15:07
• Kernel version: iBall3.4.67
• Build number: iBall Slide MJK Brace-X1_KK_V2.07,2016-01-12_19:19
• MT6592
And its RAM is 2GB and internal storage is 16GB.

To unlock boot-loader, I run in command prompt…
adb devices
List of devices attached
x.x.x.x device

fastboot oem unlock (after this command, I confirmed on tablet screen by pressing Volume Up but no changes on screen of computer and tablet. Even after 45 min, there are no changes on tablet screen and command prompt.)

I changed USB cable and plugged it in another USB port. However, no changes.

Please help me to fix it so that I can unlock its boot-loader.

Regards
Ugn10