Have you followed our instructions for cleaning the printer’s capping station, wiper blade and bottom of the print head? If not, I recommend manually cleaning your printer, and instructions can be found here: http://www.inkjetmall.com/tech/content.php?133-Printer-Cleaning-and-Preventative-Maintenance
We also have a helpful document explaining how to evaluate the health of a printer by examining the printed nozzle check, here: http://www.inkjetmall.com/tech/content.php?167-Evaluate-a-Manual-Nozzle-Check-to-Determine-the-Health-of-Your-Printer
After manually cleaning the printer, if the one cyan nozzle continues to not print, but the rest of the cyan channel, and other channels are printing well, then I recommend making a test image with dark shadows (to use the cyan/shade 2 channel), and closely examining the print to see if you have noticeable print defects (white banding) due to the missing nozzle, or if the print looks good. Sometimes, a single missing nozzle won’t show obvious problems in the print, but that’s dependent on several things, including the printer model and how many nozzles per channel it has, the paper you’re printing on, and overall health/condition of the printer.
We have several Piezography glossy curves available for download, here: http://www.inkjetmall.com/tech/content.php?158-Piezography-K7-GLOSSY-Curve-Resource
If you don’t find a curve specific to the exact printer/ink/paper you’re using, then you can try one for another ink tone to see how the results look, but if you’re not totally satisfied with the results, we can make custom curves to optimize the output for your specific printer/ink/paper combination.
I hope this helps.