Headphone monitoring

Hi,
I am having trouble getting the headphone monitoring to work.
The soundcard is a Tascam US-600, I am running CrossDJ 2.5.0 with the envivio env-1274 controller.
Both channels are coming through the headphones despite trying different settings in the preferences and clicking on/off the headphone icon at he top of the channels.
I'm sure it's something simple I have missed and would be grateful for some tech help.
Thanks,
Fin
I am having trouble getting the headphone monitoring to work.
The soundcard is a Tascam US-600, I am running CrossDJ 2.5.0 with the envivio env-1274 controller.
Both channels are coming through the headphones despite trying different settings in the preferences and clicking on/off the headphone icon at he top of the channels.
I'm sure it's something simple I have missed and would be grateful for some tech help.
Thanks,
Fin