I have had a response for SE!
From:
support_eu_ol@square-enix.com
Dear Customer,
Thank you for contacting the Square Enix Support Centre.
Following upi from our recent email conversation regarding the error 406 you reported,
We would like to ask you to please ensure that there are enough funds in the account the card belongs to and please send us an image of the card to
sel-id@square-enix.com to be able to whitelist it and for you to use it.
We apologise for any inconvenience caused.
Kind regards,
The Square Enix Support Centre team
Thank you again for contacting us and for your interest in Square Enix products!
More help and information is available at the Square Enix Support Centre website.
http://support.eu.square-enix.com/
I hope this works!