tax simply doesn't apply to product prices

Hi!

First of all I have to say that I love your extension and I like very much your customer support. You helped me a lot in the past two-three weeks with my joomla 1.6 and HikaShop problems. Now for practical reasons I downgraded my site to joomla 1.5.22 and I was able to export all my users and data to the new site with new HikaShop except one thing: the tax rate defined previously in tax management part of HikaShop simply doesn't apply to the product price. In the product page on backend I can see the tax rate, I can choose it and nothing happens with the product price, it stays as it was without adding for example the 25% tax-rate. I deleted the tax rates, tax categories, created new ones and the problem is still the same...
Do you have any idea how to fix that?

Thank you for your answer. I made a screenshot from product page on backend:

Sorry... It was my fault... In main settings tab I didn't set the Main tax zone properly...