Attempt to register for courses returns blank page

We received the following feedback from our customer.

Just signed up for a new course.

A few things I want to notice about your new site:

1. First attempt to create a new account has failed with no errors. Create account popup window just went blank ( Using Chrome )

2. I’ve payed for the course but Chrome shows that there is an insecure form on payment detail page.

3. Not sure what has happened after I’ve payed – dashboard doesn’t show when the I can take the course.

I’ve tested and am met with the same errors. This happens after the last update.