Pages not viewing on Checkout Process

-- HikaShop version -- : 2.6.2
-- Joomla version -- : 3.5.0
-- PHP version -- : 5.5.24
-- Browser(s) name and version -- : Firefox 39.0
-- Error-message(debug-mod must be tuned on) -- : Blank Screen on Firefox
Chrome: Access to www.airsoft-hq.co.za denied you don't have authorisation to view this page.
403 error.

When entering the checkout process error message pages are happening on multiple page addresses.
Blank Screen on Firefox
Chrome: "Access to www.airsoft-hq.co.za denied you don't have authorization to view this page.
403 error."
The address in the URL bar is the correct page.

When I refresh the page it views.
How do I sort this out please.