Why does Paypal say that my credit card / email address is attached to a Paypal account and ask for your Paypal password?

Paypal has recognised that your credit card or email address being already attached to a Paypal account, therefore to add security to your account it asks additional questions.

If you have forgotten your password you can ask Paypal to send it to yourself.

Alternatively use a card and or an email address which is not connected to a Paypal account.