Don't forget to set your 2nd unit to IR (infrared) mode. Here is the Harmony Information:
This DirecTV PVR / Satellite is capable of accepting RF (radio frequency) and IR (infrared) signals. To operate this device, it needs to be set to respond to an IR Remote:
1. On the original DirecTV remote press the Menu button
2. From the Menu press Select on Settings
3. Select Remote from the left menu
4. Press Select on the IR/RF Setup button
5. Use the Up or Down arrows to change from RF to IR
6. Press Select to save

Note 1: Also use the device "Confirm IR commands", as the alternate IR dataset (for address 00003) may already be in the database.

Note 2: The Harmony setup interface will probably be very busy today.