When I try to calibrate a master dark into other images in the image calibration tool I keep getting a message in purple saying "wanring: no correlation between master dark and target frames (channel 0). Do I have a setting wrong someplace?
it means that PI could not correlate the noise in the dark with the noise in the target frame. this can be due to any number of problems: the ISO doesn't match between the light and dark, the gain or offset doesn't match between the light and dark, the lights and darks are so short that there's barely any dark signal in either, there is a huge temperature or time mismatch between the lights and darks, etc.
we need more information about what kind of camera you are using, how long the darks and lights are, the temperature of lights and darks...