Originally Posted by drscoop

Yes, ESTA up to date and a shiny new passport too. Wondered if that might be the issue - travelling on a new passport?

Have pritend off the "detail complete" form and the filled in API page. Interestingly, after printing I got a "cannot find booking" error. Logged off, on again and, lo and behold, all the API had been wiped out. I have re-entered it all and saved it again. Let's see what happens next...!