Forget and rejoin
System Settings → Wi-Fi → Details on the network → Forget This Network. Rejoin and enter the password once. Do not save three copies of the same SSID.
Mac will not stay on Wi-Fi
macOS dropping Wi-Fi is often a stale preferred-network list, a captive portal, or 2.4 GHz vs 5 GHz confusion. These steps are safe and reversible.
Turn off private Wi-Fi address temporarily
On the network’s details, disable Private Wi-Fi Address if the router uses MAC filtering or a small DHCP pool. Re-enable it after you confirm the join works.
Renew DHCP
System Settings → Wi-Fi → Details → TCP/IP → Renew DHCP Lease. If the IP starts with 169.254, the Mac never received an address from the router.
Wireless Diagnostics
Hold Option and click the Wi-Fi icon → Open Wireless Diagnostics. Note the signal (RSSI). Values weaker than about −75 dBm at the desk mean a placement or interference problem, not a software bug.
When to get TechMax involved
If only one Mac fails while phones work, or the Mac joins then drops every few minutes, a remote session can inspect location services, VPN profiles, and the Wi-Fi plist without wiping the machine.
Need this done with you on the line?
Start a LogMeIn Rescue connection with the PIN your TechMax technician provides.
Start support connection