macOS Sierra: Troubleshoot connecting to the Internet
If you’re having difficulties connecting to the Internet, you can use Network Diagnostics to help resolve the problem.
To open Network Diagnostics, choose Apple menu > System Preferences, then click Network. Click Assist Me, click Diagnostics, then follow the onscreen instructions.
If Network Diagnostics doesn’t resolve your connection problems, try the following suggestions.
Wait a moment, then try again. Your ISP may be having problems. If you continue to have problems, contact your ISP.
Open Network preferences and check the status of your network connection services, such as Ethernet or Wi-Fi. Green indicates the service is active (turned on) and connected. Yellow indicates it’s active but not connected. Red indicates the service has not been set up.
Compare your network settings in Network preferences with those recommended by your ISP. Make sure you have the latest settings entered in the appropriate fields.
If you’re using PPPoE, make sure nothing is entered in the PPPoE Service Name field (in the PPPoE pane of Network preferences). If your ISP requires a setting in that field, verify that you’re using the correct information.
If you understand networking fundamentals, try using Network Utility to investigate the problem.
If you’re using a telephone modem, try dialing your ISP’s modem number using a regular telephone to check if the ISP’s modem answers and to check the line for static or other noise that might interfere with the connection. To monitor the modem as it tries to connect, turn on modem sounds. Open Network preferences and select your modem service in the list. Click Advanced, click Modem, then select Sound: On.