MacBook Air won't connect to WiFi

First step, go into System Preferences > Network > WiFi > Advanced. In the Preferred Networks list, delete the network you are having problems connecting to. Apply the changes & exit. Also remove that new Location you created. Then restart your Mac. Then try to reconnect to the network.

Note: if you are running macOS Ventura or later these settings will be under System Settings and the sequence may be slightly different but the objective is the same, that is to remove the offending network from the preferred list.

Al Lemieux wrote:

Finally, I moved the laptop to within 1 foot of the router and retried and it connected and the connection stayed and the IP address resolved. Do you think the WiFi component is somehow compromised?

That at least proves that it can work. But you should not have to be that close to your router for it to work! You should be able to be 20' or more in the same room.

Are you using a 5GHz network or a 2.4GHz network? If you don't know, connect to WiFi, then Option-click the WiFi icon in the toolbar and look for the channel number; if the channel number is 32 or higher then you are on 5GHz. 5GHz is not as strong a signal as 2.4 GHz channels 1-11. It's possible that may be a factor and you could try connecting to the 2.4GHz network instead - almost all routers provide both 2.4GHz & 5GHz.

If you have an Intel Macbook Air you could try resetting the SMC. Note this is only Intel ... M-series Macs don't have SMCs or NVRAM; a full shut down resets similar things on M-series Macs.

Since your MacBook Air has a self-assigned IP, try these steps: 1) Forget the network in Wi-Fi settings, then reconnect. 2) Reset your Network settings (System Settings > Network > Advanced > TCP/IP). 3) Try removing Wi-Fi from network services, then add it back. If that fails, reset your SMC/NVRAM.