You can only find your orders in your account that are purchased using the same email address you've registered your account with. 

Have you created your account with the same email address as the one used to purchase tickets? You should be able to find all of your orders in your order overview after verifying your email address through the link sent after signing up. 

Did you purchase tickets with different email addresses? Then you need to create multiple accounts. It is not possible to merge these orders for safety and privacy reasons.

For more information please check the FAQ of Paradiso.