Lack of confirmation
I never received an email with my tickets. When I went to the train station and went to the ticket booth for Renfe, they said that since it was a 3rd party vendor, they could not assist or look up the ticket information. Before buying new tickets, I had to call customer service (in a panic) for rail ninja to find out that I needed to log back into the website, set up and account and password, and go from there. It would have saved a lot of stress if this information was shared prior. When I purchased my tickets I got a confirmation for my order, saying that I would received tickets in a separate email.