The Delta computer system is set up so that NOBODY can print your return boarding passes until you've completed the flights TO your destination.

So for instance if you managed to book A->D but routed as
A->B->C->D->E->A

When you check in initially you should get your boarding pases for
A->B
B->C
C->D

and no matter how much people try at airport B or C, the system will not allow the boarding pass for D->E or E->A to be printed UNTIL you get to D.

I had a similar situation where a CRC agent was convinced she could get the return boarding passes printed...and tried and tried and called their help line and was told the system will just now allow it.

NOW...when you get to destination, D, (in your case ATL) the gate agent for your return flight can EASILY print your boarding pass, as can a SkyClub agent (if you are a member/gain admittance).

I think this is what the various people at ATL were not clearly explaining. You could get it from your flight's gate, once "gate control" has taken place and the gate agent had complete access to the flight.

My first MR was to SJC where I arrived on a DL 737, and went right back on the same plane 1 hour later. I just asked the gate agent POLITELY for my boarding pass. She asked me how I got past security without one and I explained that I had just arrived on the flight and she smiled and said something like "I've heard of people like you..." and printed it out.

Hope this helps...thanks for posting about your experience!