It could be the airline or website / service you used for the purchase. Some have been caught up in frauds enough times so they're automatically blocked. Happened to me a few times. Usually a call to the bank sorts it out.
You can use power of attorney forms for almost everything here. Banks, government issues, etc. Never had an issue with it and you don't need to be present. Of course, it requires a party on site that you can trust with it.