I've just moved from the built-in Hue Integration to CocoHue and seem to have a strange issue with a group. I have imported 2 Groups into CocoHue, both contain 2 bulbs (Porch=colour, Hall=white)
Try running a Set Color or Set Color Temperature command on the problematic group to make sure all attribute get populated, even though it probably won't do much with the actual devices, then try again.
Great! Note that if this is a White Ambiance bulb, you'll now want to change the activation mode to CT (or Switch or Dimmer), since RBG will likely not work.