Foreign Ticket Verification problems

My Chinese friends are helping me buy train tickets for an upcoming trip but because of the Chinese New Year travel time, I have to buy multiple tickets to get to where I need to go. I had bought four tickets, three for going to and one for returning, however I needed to get one more ticket but it wouldn't let me saying I need to verify my passport since I bought four tickets. I had my friend cancel one of them so I would have less than four but it still won't let me buy anymore. Any help or thoughts appreciated.