We've had a small number of users report that they're unable to make a payment and find that the payment button is greyed out.
If you find that this happens to you please try this workaround. Start by logging into the Seatfrog app, tap account, then on the new screen 'payment methods'. From here you can add a payment card by tapping '+ new card'. Once that's done, head back to the Train Swap site, and you should be able to select the card you've just added.
If there are any problems, please reach out to our team by writing to firstname.lastname@example.org.