Hello there,
I did search to see if anybody else had this issue but could not find anything related.
So this module works fine with my existing Bootstrap 3 template, customers are taken to the authorization frame with their bank.
I have a new template fileset which is Bootstrap 4, when I switch to this template it gives 'an unable to proceed with payment' red error, and the following on admin email:-

Customer arrived on the order process page without completing required authentication.
It is like something is blocking the frame or authorisation connection, I suspect it is template related. I even tried One Page Checkout, and still the same. If I revert back to normal template everything is fine. So I suspect it is something blocking it that is sitting outside of the checkout file structure.

I do recall having this issue a few years ago when moving to a new template, but the template creator fixed somehow.

So currently the developer of the template insists it must be something my end so it isn't their issue (though I have come across one or two issues unrelated that they have had to fix).

I appreciate any pointers or guidance with this, I am certain it is this custom template. It also uses jquery and ajax. I am using PayPal Website Payments Pro (UK) version. Thanks in advance.