Why when I click on the button - "Login or Sign up" in Customer Portal, the Create Account, sign up page is not called?
Customer Portal (CP)
Do you have Pass Through Authentication (PTA) enabled for your site?
Check the configuration setting PTA_ENABLED, if it is set, you will need to disable it in order to use the "Login or Sign Up" button in CP unless you want to use Dual Mode PTA.
To use Dual Mode PTA you need to also enable PTA_IGNORE_CONTACT_PASSWORD configuration.
If you are not going to use Dual Mode PTA then you need to disabled PTA_ENABLED in order for the "Login or Sign Up" button to work on your CP pages.