Products not 'adding to cart'

-- url of the page with the problem -- : www.continuitylenses.com/en/single-boxes
-- HikaShop version -- : 2.6.0
-- Joomla version -- : 3.4.6
-- PHP version -- : 5.5.30
-- Browser(s) name and version -- : Google Chrome 47.0.2526.106

Hello,

We are experiencing an issue where you cannot 'add to cart' on:

www.continuitylenses.com/en/single-boxes
www.continuitylenses.com/fr/pak-singulier
www.continuitylenses.com/nl/enkele-doos

When you attempt to 'add to cart', the page redirects to the homepage where you receive a Joomla system message 'Your cart is empty'.

Interestingly, when you 'add to cart' from products contained within a module (HikaShop Content Module), it works fine.

Do you have any thoughts on what the problem might be?

Thanks

Hello,
Quick update:
It appears you can proceed to checkout if you select different radio buttons (monthly/daily). If you leave the settings as they were on page load (ie. 3 monthly radio button checked), it redirects to the homepage.

Changing the power or quantity make not difference it seems...

The following PHP error is generated:
PHP Notice: Undefined property: stdClass::$data in C:\inetpub\CL\plugins\system\emailasusername\template_overrides\com_hikashop\le_com_hikashop.php on line 55

Thanks

Hi,

The plugin "emailasusername" is creating an override, it is maybe this override which is causing the issue.
Could you try to disable that plugin and test again ?

Else screenshots of your product settings will allow to have more clues.

I tried disabling the emailasusername plugins but no change in behaviour (it still redirects to the home page, unless you change variant first) but the PHP error is no longer logged, so I am pretty sure that is an unrelated issue and we can ignore that here.
Attached are screenshots of one of the products in question.

Hello,
Renaming the folder you mentioned did resolve the issue. In the end I tracked it down to the show_default.php. We had modified this, which wasn't the problem, but at some point some extra line-feeds seem to have found their way in corrupting the file?!
Anyway, tidied it up and all seems to be working now...
Thanks