Add to cart popup - 404 error with SEF enabled

-- HikaShop version -- : 2.6.0
-- Joomla version -- : 3.4.5

This has been asked many times, but I can't find what causes the 404 error on the add to cart pop-up in my case.

There are 2 main menu items:
1 that navigates to the e-shop section of the site, that is a products page from all categories.
1 that is for showing categories products when selecting a category from the categories tree module.

Adding to cart from the second menu item (category's products), it works ok.
But when I try to add to cart a product from the first menu item, it shows 404 error in the popup.

The same is for when I arrive at the product page. If my path is from the main eshop menu item, it throws 404, but it works fine when I arrive to a product through its category page.

Any feedback on this?

Hello Jerome,
I emailed using the form on this website, the details of how to access the site and included a link to this thread here.

I have tried that but it didn't solve the issue.

Here is the screenshot:

Friendly bump...

Hi Nicolas,

I changed the Checkout SEF name setting to what you see in the screenshot, in an effort to make it work, because the original "checkout" name had the exact same issue giving the 404 error on the add to cart popup.

When you say customizations you mean template overrides likely? Because I am disabling completely the template overrides for hikashop by renaming the com_hikashop dir inside the html dir of the template and still I the 404 error occurs.

Any update ?

Guys ... anybody there?

Any chance to get some kind of support?

Days are passing and it seems to be no light in the tunnel - no response from Hikashop and the issue is still there.
How many days should I wait for a solution? It's now almost 2 weeks and the add to cart popup displays a 404error.
May I have some kind of prompt answer and the proper help to fix this?

This is ridiculous... you guys are totally unprofessional.