help with preview on hercules instinct with virtual dj

hi guys i wonder if you could help me with a small problem i am having. i purchased the hercules instinct which came with the djuced 18 software, everything works great including the preview.

problem i now have, is that when i switch over to the virtual dj software (7.4 pro which is mapped to hercules controller) the preview wont work and i am hearing nothing through my headphones.

is there something that i am missing in getting the hercules instinct preview to work with the virtual dj pro 7.4?

any help would be appreciated.