Unable to login to ArcGIS Pro using a numeric login created as an Esri account and added to an organization. The following error is returned, "ArcGIS Pro was not able to download license from the licensing
portal".
Do not create an Esri account with a numeric username.This issue seems to only occur when inviting existing users from an Esri account, which contains completely numeric usernames. Issue is not reproducible when a numeric username is created upon invitation to ArcGIS Online organization (i.e. "Send invitations to pre-established usernames").