I'm trying to add a group to a document library to give them permission to see it. If I type the group name and ask SP to check it, it says
No exact match was found
If I search the address book it will find the group, I presss "Add", "Ok", after about 10 seconds it adds the group name underlined. I choose the level of permission, choose whether to send an email or not and then press "Ok". The page then jumps back to the top wih the same error as above. Most frustrating!
I've successfully added an individual user to this library and edited the permissions of exsisting groups so it seems to be a problem with authenticating the group name rather than a problem with the library itself.
I've found a few similar questions on SE but I only have client side functionality
Update: One of the higher admins (who has acess to Central Administration etc) thinks it is a sync issue between SharePoint and Activve Directory
Update: I can add other groups to this library but the group I cannot add was created after the library stopped inheriting permissions, I think this may have something to do with it?