If your Mac suddenly won't connect to a working wi-fi you've used before

Occasionally you may run into an issue where a wifi network you use is unable to connect with your Mac. If you have already tried rebooting your cable modem, rebooting your wi-fi router, or in some cases you've called your provider and they find nothing wrong with your modem and they may have you reset your wi-fi router back to factory restore; and still your Mac will not connect.

In some instances you may need to remove the Wi-Fi from your list of available networks and reconnect to it.

To do this you will need admin account or need to know your admin user/pass if you are prompted, most importantly you need to know that Wi-Fi password.

in the wifi dropdown select Open Network Preferences

Click Advanced

Select the problem network from the list and click the "-" icon, then Remove the network.

if you have other devices already on that network they will not disconnect, but if you have devices that use that network but are not connected at that time you will need to know the password to for the wi-fi.

Close the Wi-Fi control panel and reconnect.

if the problem persists open the Network Control Panel again and remove the Wi-Fi connection

Select Wi-Fi and click the "-" icon

close out of the network panel and open it back up

select the "+" icon and add a new Wi-Fi connection from the dropdown

Reconnect to the Wi-Fi