Exporting a group for an offline installation generates an error stating 'Error while creating offline installation package'.
This may occur when a special character(s) is used as part of the group name. When the PolicyServer is creating the export file the group name is used as part of the exported file name. Windows does not allow files names to contain special character(s).
To addres the issue, rename the group you are exporting to a group name that does not contain special characters.