May be you have already solved your problem by now.
I found the right information from other emails in this forum.
I also have the same problem. I found you need to do a "dummy plug" installation as shown in one of the product diagram. Need to have this done in order to run on a DC layout. Replace the dummy plugs with the DCC decoder when you go to a DCC layout.
In my opinion Bachmann did a poor job in instruction and do not have a competent customer rep. I could not find the right answer by contacting their rep.