This KB article describes a workaround when compensation curves for spot colors aren't calculated in PressSync 16.0.2. In this particular case, a spot color is any other color than the standard CMYKOGB colors.
You'll get the following message after measuring a chart with spot colors: "Notes form collecting all measurement samples: A solid patch for ink xxx (pms1000c) was not measured. It will not be possible to calculate a curve based on tone measurements for this ink."
The spot color is missing in the results window (Spot Colors > Tone Measurements > All Inks).
Solved in the November 2017 release of Esko Software Platform.
Measure the chart.
Save the measurement.
Open the it8 file with a text editor.
Add INKSET 22 below the PROCESSCOLOR_ID "pms1000c/Violet" line.
Save the it8 file.
Click the Cancel button.
Remove the existing measurement data by selecting it and clicking the Remove button:
Click the Measured Data… button and load the modified it8 file.