Your account could not be used to authorize ArcGIS Pro because it is an ArcGIS Public Account

Error Message

Attempts to sign in to ArcGIS Pro fail, and return the following error message:

Error:   
Your account could not be used to authorize ArcGIS Pro because it is an ArcGIS Public Account.

Cause

The issue occurs because the account used to sign in to ArcGIS Pro is a public ArcGIS Online account. Refer to ArcGIS Pro: Your account is an ArcGIS public account for more information.

Solution or Workaround

To resolve the issue, convert the public account to an ArcGIS Online organizational account. Choose one of the methods provided below.

Join an ArcGIS Online organization

Note:
Only administrators can perform this workflow.

1. Invite the user with the public account to the ArcGIS Online organization. Refer to ArcGIS Online: Invite and add members for steps to do so.
2. Assign an ArcGIS Pro license to the user. Refer to ArcGIS Pro: Manage licenses for more information.

Create an ArcGIS Online organizational account  

Note:
Creating a new ArcGIS Online organizational account requires an ArcGIS Online subscription. For more information on ArcGIS Online subscriptions, refer to Esri Customer Service. After purchasing a license package such as ArcGIS for Personal Use or ArcGIS for Student Use, the ArcGIS Online subscription must be activated before assigning an ArcGIS Pro license to the user, and signing in to ArcGIS Pro.

1. Activate the ArcGIS Online subscription using the link in the 'Activating your ArcGIS Online Subscription' email. Refer to ArcGIS Online: Activate subscription for more information. Alternatively, obtain the subscription activation link from Esri Customer Service.
2. Assign an ArcGIS Pro license to the username created in Step 1. Refer to ArcGIS Pro: Assign ArcGIS Pro licenses in ArcGIS Online for steps to do so.