When purchases occur within seconds of one another on the same credit card, this can sometimes raise red flags for both your bank and also the train/bus carrier on potential credit card fraud.
If this is detected, your bank and the train/bus carrier will halt your card for your security.
What can you do?
Call your bank and let them know that you are attempting to purchase tickets in multiple transactions and authorize the charges to go through.
When trying again, we suggest waiting 15 minutes, and using a different internet browser or clearing the cache and cookies from your current internet browser as to erase the prior failed attempts.