Product Options - Variants

-- HikaShop version -- : 3.0.0
-- Joomla version -- : 2,5

I have products showing correctly on the website with options showing. Each of the options is showing the option name plus price which adds ok at the checkout if someone orders a product plus a variant.

Problem is now I need to update the price of one of my products options, but in the product admin page I cannot find anywhere where I can change this. The characteristics are there. In the product page, it is showing 2 items under options in the specifications group. But there is no variants tab showing on the product page.

Is this because I have had these products here for a number of years without change?

Thanks - its been awhile since I have had to change