When I try to access the App Store, up pops the message 'cannot connect to the App Store' what do I need to do to get access?

I am feeling very frustrated because I am unable to get access to the App Store on my laptop, as the message pops up ' cannot connect to App Store'. Unfortunately when I first bought the laptop I had no need to use this app. But when I did, my lap top was out of guarantee! I haven't the money to spend a fortune with apple to have it investigated. I would love to use Facetime but of course need to download the app, which I cannot - I can access the App Store through itunes but can't buy Facetime app via itunes. Any suggestions please?