When a group profile is exported it is only the group profile itself that is exported and not the profiles that are in that group. Therefore when you import a group profile it will be empty unless you also firstly import one or more profiles that are part of that group. Empty group profiles are not displayed (they are in fact automatically deleted as part of the internal 'housekeeping'). Import the profiles that are in the group before importing the group profile itself. If your profiles are all imported now, but one or more Groups are missing, you usually only need to repeat the group profile/s import to 'recover'.

Refer to this export/import article for additional tips on importing group profiles.