A user assigned to a custom role having all administrator and general privileges is unable to invite members from outside the organization to a group.
Last Published: October 31, 2014ArcGIS Online
Bug ID Number
October 14, 2014
March 30, 2022
After review by the development team, it has been determined that this issue is related to a known limitation with the software that lies outside of Esri's control. The issue's Additional Information section may contain further explanation.
This is as designed. A user assigned to a custom role can only invite users outside the organization only if he or she is the owner of the group.
A user assigned to an Administrator role is able to add or invite users outside an organization.