Siemens Siprotec device fails to communicate when using DNP3

I'm attempting to read the values out of a Siemens Siprotec 7UM622, but I'm experiencing trouble with the communications. I have verified the connection settings (baudrate, data bits, parity, etc) as well as the physical wiring, but I'm absolutely stumped.

Enabling logging on my DNP3 Master, I see that I am successfully transmitting my requests, but I am not receiving any data back.

[07:00:42.625] Tx => 
05 64 05 C0 01 00 64 00 59 97                  .d....d.Y.     
[07:00:48.640] Tx => 
05 64 05 C0 01 00 64 00 59 97                  .d....d.Y.     
[07:00:54.656] Tx => 
05 64 05 C0 01 00 64 00 59 97                  .d....d.Y.     
[07:01:00.671] Tx => 
05 64 05 C0 01 00 64 00 59 97                  .d....d.Y.     
[07:01:06.671] Tx => 
05 64 05 C0 01 00 64 00 59 97                  .d....d.Y.     
[07:01:12.687] Tx => 
05 64 05 C0 01 00 64 00 59 97                  .d....d.Y.

DNP3 isn't exactly my forte so any input as to what could possibly be causing this break down in my communications would be helpful.