Volume switch on Keystation 61es not working

So, it's my first thread here, I'm hoping I'm doing this right.

I use my Keystation 61es with VSTs on FL Studio.

But when I try to change the volume directly on the Keystation nothing happens

The only volume control that works is the speakers and the FL Studio's.

I just wonder if this is normal or if I could do something to enable the controller's swith.

In the case my signature doesnt appears:

Mainboard : Intel Corp. DG41WV
Chipset : Intel G41
Processor : Intel Pentium E2140 @ 1600 MHz
Physical Memory : 4096 MB (1 x 4096 DDR3-SDRAM )
Video Card : Intel(R) G41 Express Chipset
Hard Disk : Western Digital WD3200AAJS-00L7A0 ATA Device (320GB)
Operating System : Windows 7 Ultimate Professional Media Center 6.01.7601 Service Pack 1 (64-bit)
DirectX : Version 11.00
Windows Performance Index : 2.8 on 7.9