This information applies to all versions
This error occurs when a plug-in is launched from the Nik Collection Palette (formerly known as Nik Selective Tool) before an RGB image is opened. Open an image before accessing the plug-in in order to prevent this error.
If you already have an image opened, then make sure it is an RGB image file and not a CMYK or Grayscale image, as the plug-ins will only open images using the RGB color space.