trying to add new shipping address during checkout 403 error

-- url of the page with the problem -- : buzzyb.com.au/dev/checkout/checkout/layout-step
-- HikaShop version -- : 3.3
-- Joomla version -- : 3.8.5
-- PHP version -- : 7.2
-- Browser(s) name and version -- : Opera 50.0.2762.67
-- Error-message(debug-mod must be tuned on) -- : 403
**ACCESS FORBIDDEN.**
The page you are looking for was moved, removed, renamed or might never existed.

When I am trying to add new shipping address during checkout, after address is entered and "tick" is clicked I get the error:

403
**ACCESS FORBIDDEN.**
The page you are looking for was moved, removed, renamed or might never existed.

Checked similar posts before, nothing helped so far. This is relatively new site, so not sure if this ever functioned before.
Everything under /dev/ is a development version, so feel free to try it.

Thanks Nickolas!

It worked!