I cannot connect to my Wi-Fi after plugging my Macbook Air into the Ethernet. What seems to be the problem?

System Setting >> Network in sidebar

As the wording in below image >> Drag the presented Network Interface into the Order you what

In my case Ethernet is Preferred and Wifi is second

If you what Wifi as Preferred Drag to Top of List

Normally, you usually connect via One method or the Other but you can have both working at the same time

Disconnect the Ethernet cable form the computer

Check if your WIFI connection has joined your Home Wifi signal

Stll does not get a connection to surf the internet.

Unplug the Router form the electrical and wait 30 seconds

Re plug in the router and wait for ALL the lights stop flashing and are ON

Try your Wifi again

The Ethernet has nothing to do with Wi-Fi. They are two separate methods of connecting to the Internet.