I think I’m connected to the internet, but nothing seems to be working…

If you’re on Ethernet, go to System Preferences > Network and select your connection on the left. It should report that the connection is active and has an IP address. (For a Wi-Fi connection, access these details by clicking Advanced, then TCP/IP.) If not, turn the connection off and on, or reset your router – see “What should I do when my Mac won’t connect to the Internet?” opposite. If all’s well, check the system status page on your internet service provider’s website to see if it has a fault.