I'm facing same issue while some days.
I'm unable to share my maps or layer with my group. It sometimes said that i haven't an avaible group.Or there is required quality before sharing with group? thanks before
Have you checked the help? There is a link on Sharing
ArcGIS Online Help | ArcGIS
under the title banner, is the links to Use, Create, Share, Administer and Apps
That is where you are most likely to get help. There are the links to administrator documents which i presume you have seen if this is not just a personal account
You may this link in the help documents regarding sharing items to a group with the capability to update items helpful.
Retrieving data ...