Hello,
I had the same problem, but found the solution. I am using 6.0.6. In my case I had an existing card en what I did is go to the website, fill in the fields manually and then I saved the form again form the Assistant. It asked for update the existing, what I did. The there was a Button called [Webform] which holds the additional info. Now if I go to the website it will fill in all 3 fields.
Stupid that they did not mentioned it in the release notes!.