Hi @elena_elena,
Welcome to the Auth0 Community!
First, I would like to clarify that toggling on the Custom Login Page switch will override the New Universal Login experience with the Classic Universal Login experience. You will also notice a yellow banner appear when the switch is toggled on. See below.
In this case, you will need to disable the Custom Login Page switch and custom the New Universal Login page following the documentation here. Doing so will allow you to continue using Organizations and customize your New Universal Login pages.
Please do not hesitate to reach out if you have any further questions.
Thank you.