No forwarding to Product page

-- url of the page with the problem -- : www.alphatrainingservices.co.uk/tabs
-- HikaShop version -- : 2.3.0
-- Joomla version -- : 3.2
-- PHP version -- : 5.3.3
-- Browser(s) name and version -- : Firefox 29
-- Error-message(debug-mod must be tuned on) -- : Error_message

Good morning,

I`m having a problem with Products page. If you will go to following website:
www.alphatrainingservices.co.uk/tabs
Let`s say click on slider on first tab ( First Aid tab ) "First Aid" and then click on link First Aid at Work just next to price you should be forwarded to product page website, however I get empty page. It was working fine today, however not anymore. It`s started after I was playing with Paypal payment options ( I was adding, changing it ) then I played with SEF in Hikashop. Now I can`t reverse it.
Any thoughts?

Please help.

Just to add. When I use following link:
www.alphatrainingservices.co.uk/index.ph...e=&Itemid=14&lang=en

It works ok, so it needs to be SEF, but how to go back to proper SEF?
Please help