Problem statement
When more than one database connection is enabled for an Organization, users can only log in using one of the database connections. Users in the other database connection fail to authenticate.
Symptoms
Users from database connection A can login, but users from database connection B can not.
Cause
Whenever more than one database connection is enabled for a given login transaction using the New Universal Login page, Auth0 needs the connection querystring parameter to be sent in the /authorize request to tell it which database connection to use to log in the user. Otherwise, it will default to the first enabled database connection.
When using Organizations, the connections enabled for the Organization supersede the application’s (client ID’s) enabled connections. Even if an application has only one database connection enabled, but the user logs into an Organization with two databases enabled, the latter will override the client ID’s configuration.
Solution
When an Organization has more than one database connection enabled, a connection parameter needs to be sent, in addition to the /authorize endpoint, to allow the Universal Login page to use the right database connection.
See the Login documentation for more details.