DNP printers on Mac default to the wrong paper size and will not print. To fix this, go to dslrBooth, File, Print Settings... and change Paper Size to 6x4 from the drop down then change Orientation, then save. If you print and find that your image is rotated, change the Orientation again.
The following shows what these settings like like for the DNP DS-RX1. Your settings may vary slightly.