When a user with the administrative privilege to manage the organization's collaborations attempts to start a partnered collaboration with another ArcGIS Online account, the following error message is returned:
Error: An error occurred. Unable to send the invitation.
The other ArcGIS Online account is not an ArcGIS Online organizational account.
Partnered collaborations are only available for subscribed ArcGIS organizations, and are not available for developer and individual accounts such as public, trial, evaluation, and ArcGIS for Personal Use accounts. To start a partnered collaboration, an ArcGIS Online organizational account type is required for the accounts initiating and receiving the partnered collaboration request. Refer to ArcGIS Online: What are the ArcGIS account types and where can I use them? for more information on ArcGIS account types.
Refer to ArcGIS Online: ArcGIS Online Pricing for more information on purchasing ArcGIS Online subscriptions. Refer to ArcGIS Online: Activate subscription to activate an existing ArcGIS Online organization subscription.