2checkout

-- url of the page with the problem -- : 3d.atoa.com
-- HikaShop version -- : 2.5.0
-- Joomla version -- : 3

I used an external 2checkout plugin and at the checkout when I complete the form and submit it takes me to 2checkout payment page,It asks for billing address once again in 2checkout, whereas I already filled billing address on the hikashop checkout .

Hello,
Are you using the 2Checkout payment plugin developed by MintJoomla ?
if that's the case, you'll have to directly ask it to them, because it's the plugin which is supposed to send that kind of information to the Payment platform.