Auto-generated password for new user registration is not displayed ?

If you choose to customize the field "Introduction for customer new account email" with a custom text to welcome your users. You must include somewhere in the text the placeholder {{user_pass}} so it will display the actual password to your user. You can also use {{user_login}} to display the actual user login.

For instance :

Thank you for creating an account on {{blogname}}. In order to connect to our website, please use the following credentials :

Login : {{user_login}}
Password : {{user_pass}}