Upgrade to v2.4 , no access to shop

-- HikaShop version -- : 2.40
-- Joomla version -- : 2.5.17

Hi,
Have just upgraded to v2.4 business, and for some reason, there is now no access to the shop. Clicking on a category icon refreshes the page, but allows no access.
There was a similar thread regarding checkout doing the same, but no posted resolution.
brspools.co.uk/_testing_site/index.php/shop/browse-our-shop

** Update to this question : I've turned off SEF URLs, and it seems to work..**

Can you help please?

Hi,

Please make sure that the option "Activate smaller URLs" option of the Features tab of the hikaShop configuration is turned on.