DJ707M Master Out + Headphones issue

hi 

i am running a DJ707M on Serato 2.3.7 + iOs Mojave 

my controller is about 3 months old and everything was working fine until recently. 

I turned it on for the first time in about 3 weeks and now am unable to get any signal in my master channel or headphones. 

the controller is otherwise working fine - the platter and other buttons are responsive between the controller and software.   

I can send a signal from Serato into any channel and its showing its active with LED's lighting up on channels 1 - 4 however i cannot get any audio showing on the master

I also cannot hear anything through my headphones on master or on any channels i choose to CUE.  these headphones have been tested on other devices and work fine also.   

any thoughts on what might be causing this would be appreciated.

thanks!