problem solved partially, i figured out that on private post the selection isn't working at all, if i change the post to public the add to cart button is shown after i made a selection
but the problem is still remains, after i'm going public with the post and select an atribute whihch is the other price than default one "from 10 eur" for example...the price isn't actualised (each attribute defined has a price and a stock number in variations tab)
i can mention that some of fields are missing from general tab such as Price (but i've changed in variations ) and SKU, i don't how can affect this, but the actual problem is that the price it isn't modifying after i am selecting a variation with a different price, can you help me with this please?