Turn Wi-Fi off and on, forget the network (System Settings → Wi-Fi → ⋯ → Forget) and rejoin, turn off Private Wi-Fi address for that network, disconnect VPNs, renew the DHCP lease, restart the Mac and router, and update macOS.

What's going on

If other devices work on the same Wi-Fi, the Mac’s saved configuration, VPN or security software is usually responsible. macOS includes Wireless Diagnostics (hold Option and click the Wi-Fi icon) to test connections.

Symptoms

  • Mac can't join a known network.
  • Connected but no internet.
  • Wi-Fi drops repeatedly.

Why it happens

  • Stale saved network.
  • VPN or security profiles.
  • DHCP lease problems.
  • Router compatibility or interference.

Try these fixes

  1. Forget and rejoinSystem Settings → Wi-Fi → Details → Forget This Network.
  2. Private Wi-Fi addressIn Details, set it to Off/Fixed to test with MAC-filtered routers.
  3. Renew DHCPDetails → TCP/IP → Renew DHCP Lease.
  4. Disconnect VPN/profilesCheck System Settings → VPN and Privacy & Security → Profiles.
  5. Wireless DiagnosticsOption-click the Wi-Fi icon → Open Wireless Diagnostics.
  6. Restart Mac and router; update macOSInstall pending updates.
Check it's fixed: The Mac connects and loads web pages consistently.

Avoiding it in future

Keep macOS and router firmware updated.