This looks like a concern.
You might want to delete the cache/ cookies and check if the application is updated and try to rebook.
Mostly, in case of failed transaction try using different mode of payment or changing the interface. i.e switch to mobile application or website visa versa.
Please share the contact details (email id and contact number) entered while transacting and the error screenshot if any at firstname.lastname@example.org or via LIVE CHATS.