I'm flying UK for the first time, so have no prior experience with the airline. I'm flying DEL-PNQ later this month and received an upgrade offer from Y to PE or J. I want to purchase the upgrade to J, but every time I enter my payment details on the PlusGrade website, I get an error message "There has been an error trying to submit, please try again." I've tried multiple times with no success. The issue seems to be on PlusGrade's end, as I confirmed with my credit card company that they're not even receiving the authorization request. Is this a known issue with UK's upgrade process? Anyway to address it?