Hi,
But the problem is that we can't modify anything in the Authorize.net website.
If they don't have an automatic redirection, we can't do anything in HikaShop to change it.
You can contact Authorize.net in order to have more information but in our side we can't do anything because it's not in HikaShop and not in your website.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.