Greenland can't join FIFA because not enough grass grows there.
Oh, name-based irony. You never fail to amuse.
Until 1979, Greenland was part of Denmark as a colony and had limited autonomy. Since 1979, Greenland has tried to develop more autonomy and has attempted to be recognized as an actual nation. One of the ways it has tried to do this is through sports.
The Greenlandic Federation of tae kwon do, badminton, handball, volleyball, biathlon, and table tennis have gained full membership into the International Federation.
However, the same can't be said for soccer. Apparently Greenland isn't green enough to be part of FIFA. Executives claims that the lack of proper grass and the weather conditions of the country make it unsuitable to play and practice soccer in, and therefore it cannot grant Greenland entry into FIFA.