Put 3D Secure authentication page in an iframe
It is common practice to put the 3d secure authentication page in an iframe so that the shopper has some re-assurance.
Many merchants also include reassurance messages around the iframe and also some back buttons in case there is a problem with the authentication (very occasionally the card issuer;s server could be down)
Its not common, it has been required by the card networks for some time !!!!
You will see both of these guides instruct the use of iframe and not what you have implemented.
Mastercard even say "one approach, inline windows, is now acceptable for deployment. and existing merchants are expected to convert to an inline window implementation."