Update cart in 3.1.0 non-legacy mode does not work

-- HikaShop version -- : 3.1.0
-- Joomla version -- : 3.7.2
-- PHP version -- : 7.0
-- Browser(s) name and version -- : Any
-- Error-message(debug-mod must be tuned on) -- : example.com/webshop/product/updatecart/add-1/cid-1?tmpl=ajax 403 ()
(anonymous) @ VM4843:1
xRequest @ hikashop.js?v=310:217
addToCart @ hikashop.js?v=310:885
onclick @ strassburg-sock:444

I am cuurently testing my site on a test domain to prepare for Hikashop 3.1.0. In legacy mode all seems to work (except that I cannot empty the cart), but my main problem shows when I use the non-legacy Add to cart functionality.
Then nothing happens and a Javascript error is shown in my inspector:

Failed to load resource: the server responded with a status of 403 ()
POST example.com/webshop/productupdatecart/add-1/cid-1?tmpl=ajax 403 ()
(anonymous) @ VM4843:1
xRequest @ hikashop.js?v=310:217
addToCart @ hikashop.js?v=310:885
onclick @ strassburg-sock:444

Note that the site is in an .htaccess protected area, so let me know how to give you access if needed. (and I tested whether the .htaccess is not actually responsible for the error, which it isn't)

Hi Jerome, perfect, that was the issue. I have now added ajax to the List of allowed tmpl= keywords in Admintools and all seems to work really nice mow, including the emptying of the cart.

Just one thing that users might miss: I am working on a pretty wide screen now and the notifications in the upper-right corner coulkd easily be missed. Especially showing errormessages should really be more obvious I think. See attached the screenprint of an action where the user needs to select a size for the product. I really think users could miss this:

Ok, thanks for clarifying, pop-up mode works fine for me. Thanks for clarifying, all set to upgrade now