I never had this problem prior.  I started a new project, inserted the usual downloaded AD2 template and all 10 AD2 tracks assign themselves to individual drums.  I can drag a beat over to the AD2 midi track and it will play the drums.  However, if I try to get a piano roll/drum map, it  comes up with a piano roll (no drum map) with NO MIDI NOTES in it, even though it will play.  Huh?  The output of the AD2 midi track is assigned to "5 Addictive Drums 2".  If I change that to (as suggested in Help) to "DM1 AD2 standard" the drum sound is routed to Zta3a, and the piano roll reverts to the desired drum map, but there are NO notes shown in the drum map!  WTF!!! If I go into Drum Manager for "DM1 AD2 Standard" the output port is locked to Zt3a, and there is no apparent way to change this to route the port to AD2.  Huh?  I'm stuck.

You can and should change the output port of the drum map - it will default to the first available output port. Hold Ctrl+Shift while changing one to change them all.

In Preferences, MIDI, Drum Map Manager, it will NOT let me re-assign the output port.
 
If I delete all the drum maps in Drum Map Manager, and then say New and point to the AD2 drum map, the same thing happens, in that the output port defaults to Zta3 which cannot be changed.

What do you see when you click the black inverted triangle at the right-hand end of the Out Port column to expand the output list? Or do you not see the triangle?
 
P.S. You can get there a little more directly by choosing Drum Map Manager in the Output pick list of the MIDI track.
 
Here's a screenshot from an older version I Googled up for reference:
 

OK, I figured it out.  Thanks.  Here's the way the drum map manager should look with AD2 (just in case someone else gets all balled up).
 https://drive.google.com/file/d/0B5NGFo_mTbPOMFhLbWluRU4zX1E/view?usp=sharing
 
I wonder why this problem never happened before.