Solve internet connection problems on Mac
If you can’t connect your Mac to the internet, there may be a problem with your cables, your devices, your network settings, or your ISP (internet service provider).
Check Wi-Fi recommendations or use Wireless Diagnostics
If Wi-Fi issues are detected on your Mac, you can view the issues and suggested solutions. Click the Wi-Fi status icon 
in the menu bar, then choose Wi-Fi Recommendations. Wi-Fi recommendations aren’t available for enterprise networks or Personal Hotspots.
You can use Wireless Diagnostics to solve problems with a network you’ve already set up.
Check your Wi-Fi connection
If you usually connect to the internet using a Wi-Fi network, make sure you’re connected to the Wi-Fi network.
If you’re connected to the Wi-Fi network but you can’t connect to the internet, there might be a problem with the network’s internet connection. If you set up the Wi-Fi network using an AirPort device (such as an AirPort Extreme), you can get information about the device and its internet connection by using AirPort Utility. For more help while using AirPort Utility, choose Help > AirPort Utility Help.
Check the status of your network connections
You can check your settings and the status of each network service, such as Wi-Fi, Ethernet, and Bluetooth®, in Network settings.
On your Mac, choose Apple menu 
in the sidebar. (You may need to scroll down.)
The network service you’re using should have a green indicator and the word “Connected.”
To view more information about your network service, click to select it.
Check your cables and external devices
Make sure all cables are properly connected. If you’re using an external modem, be sure one cable firmly connects the modem to your computer, and another connects the modem to a working wall jack.
Check that all external devices such as modems, hubs, and routers are plugged in, turned on, and have started up completely. Try resetting these devices by unplugging them for a couple of minutes, then plugging them back in.
Check the indicator lights on the device to see whether it’s registering a connection to the network and to your computer. If an indicator light does not come on, refer to the documentation that came with your device or contact your ISP.
Check your internet service
If all of the above are set up correctly and you still can’t connect to the internet, call your ISP. There may be a temporary problem with the service.