my photo favorites album is greyed out

I have routinely been putting pictures from the camera roll into the "Favorites" album of my iPhone 6 without any problems. Then one week ago, the Favorites album became greyed out so that I am unable to add any pictures to it. I have tried hard resetting the phone without success. I also cannot seem to find anyone complaining of a similar issue on the internet. Can anyone suggest a fix for me? I am using iOS version 8.1.3.