There are a few places here where something could happen. I would start trouble shooting at the beginning. Make sure you have audio coming out of DT/DN, then check that you have audio coming out of 404, then check on the DT/DN that you can hear the audio coming into those inputs, then hook it up to your computer and check that you can get it into your computer through Overbridge.
If you can nail down at exactly which stage the issue is occurring, it will be easier to find the solution.