From:
https://discussions.apple.com/threa...260486424022&sortBy=newest_first#260486424022
Please try this
Check date and time and update macOS
Make sure that the
date and time are set correctly on your Mac.
If you can connect to the internet from a different Wi-Fi network, connect to that network and then
update macOS on your Mac.
Check VPN or other security software
If you installed VPN or other software that monitors or interacts with your network connections, that software could be affecting access to the internet.
Learn about network issues related to VPN and other software.
Use the built-in diagnostic tools
Wi-Fi Recommendations. Click Wi-Fi in Control Center or the menu bar and check for a menu item named Wi-Fi Recommendations. If you see it, your Mac has detected an issue and has recommendations. Choose Wi-Fi Recommendations to learn more.*
Wireless Diagnostics. Press and hold the Option key on your keyboard while clicking Wi-Fi in Control Center or the menu bar, then choose Open Wireless Diagnostics from the menu. Learn more about
using Wireless Diagnostics to analyze your wireless environment.
Update the Wi-Fi router
If you manage the network's Wi-Fi router, install the latest firmware updates for the router, as recommended by its manufacturer. It might also help to simply restart the router and use Apple's
recommended settings for Wi-Fi routers and access points.
Try a different network or contact your ISP
If you can access the internet when connected to a different network, or you're not sure, check with your internet provider or network administrator to make sure that your network is working properly and there isn't an internet service outage.]