Hi Seoyoung choi! Welcome to the NS Community. 

When you order an e-ticket, it can take up to 30 minutes before your order is fully processed and you can use the e-ticket. Did you wait at least 30 minutes before you ordered another e-ticket? If you are still unable to use the e-ticket after waiting those 30 minutes, you can contact Customer Service. Did you try and reach out to the Customer Service? They are happy to help you. This can often be resolved within a few minutes.

As described in the terms and conditions of the e-tickets, a refund is no longer possible after ordering an e-ticket. The right of withdrawal does not apply to this ticket.

The problem wasn't the waiting time. Seoyoung Choi purchased an off-peak co-travel ticket while travelling in peak hours.

Though I don't really understand what happened and what you planned to do. I see three tickets with different journeys.

The 30 minutes waiting time is nowhere to be found in the terms and conditions by the way.

The app clearly says that a ticket can be opened in the app after payment. If you can't open the ticket in the app directly after payment, then that's a bug. The e-mail may take longer.

However, this was not the issue here, as far as I can see.

mrfreeze and rvdborgt  are right. This is not an exact duplicate, but two different e-tickets because one e-ticket could not be used during off-peak hours. As I indicated in my previous message, there is no right of withdrawal possible on this ticket.