Unable to login CSP page

Things to check in your web application configuration are the security and session settings for that CSP application: users may need the required application resource, the application’s allowed authentication methods must match how they log in, and session handling is controlled by options such as Use Cookie for Session, Session Cookie Path, and Group by ID if authentication is shared across applications. [1]

If the problem happens when moving from one page or web application to another, the session can also be affected by the application boundary, because authentication sharing across multiple web applications uses Group by ID. [1]

If you are using a custom login page, the login page is typically loaded before the user is authenticated, so it runs under CSPSystem. In that case, CSPSystem must have sufficient privileges to load and run the login page code, generally including READ permission on the resource protecting the database where that login page class is stored. [1][2]

A reported cause of being unable to stay logged in after an upgrade or configuration change was the web application setting Prevent Login CSRF Attack being enabled; in that case, turning it off resolved the login problem for that application. [3][4]

If you created your own login page, it should be a subclass of %CSP.Login. [5]

Important:

When creating a custom login page, you must use a subclass of %CSP.Login. Other approaches for creating login pages in CSP applications can cause problems of various kinds. [5]

Sources: