no connection to itunes store
I am experiencing error mesages and security messges 'cannot verify website' when connecting with apple store. Internet and itunes working on other devices. Not working on macbook air, OS X 10.9.5, itunes 12.3. Troubleshooting not worked, believe I need to upgrade but cannot access software upgrades due to above problem. Help -what next
MacBook Air, OS X Mavericks (10.9.5)