Hi,
I did try to reproduce the problem on your website a few minutes ago but I couldn't.
Now that the plugin is enabled, when I register on your website, it goes through the HikaShop registration form which already has an address form and that address form automatically creates an address that will be both a billing and a shipping address.
So then, step 4 of your instructions becomes non applicable as I already have the addresses filled:
monosnap.com/file/jDhoC9FZAhZd0doTR1IZxR8BMuEqM1
And then, after step 5, I directly arrive to this page:
monosnap.com/file/C5c1LeyDQe8w5LhJ7CM4JjXRjCpkAa
So again, it is non applicable as I already have both a billing and a shipping address prefilled.
To me, what Mohamed proposed does fix the problem you had. But maybe I'm missing something ?
Now, regarding the possibility to have a checkbox to use a new billing address also as a shipping address and vice versa on the address manager of the user control panel of HikaShop, like there is on the address selector of the checkout, that's a good idea of improvement. However, I can't consider this as an issue.
Note though that I've seen an issue with your template which hides the checkboxes on your website:
monosnap.com/file/qt5tUFOi7EYwaXh9rt5sXLlNmbmndH
So because of CSS in the template, the checkboxes are not visible which can be quite problematic.