DAQmx Physical Channel VI not showing any Digital Output channels

Hello,

I'm trying to output 4 identical digital voltage wave forms simultaneously using DAQmx VIs. I'm running my labview code on a NI DAQPad-6259, and wanted to specify the physical lines to output my voltages to. The problem I hit is that the DAQmx Physical Channel constant does not seem to recognize any digital line, input or output. It does recognize the analog channels, and if I create a task to generate a voltage it recognizes the DO lines, but when it runs it gives me an error proclaiming that the DO lines I set in the task aren't real.

Thanks for any help on explaining this.