It's possible the mixer does not like the unbalanced jack - you could try to use an XLR adapter
http://www.bhphotovideo.com/c/product/1 ... 3_Pin.html
Although this one I do not believe is a true converter/transformer. If like stated you aren't in the correct jack, then it won't work at all, if you are in the 'line' jack and still not getting sound (I am assuming you have the gain & level control turned up on the channel), then try to stick it into one of the stereo channel 7/8 or 9/10 MONO jack. If this still doesn't work, you possibly have a defective mic.