Macbook air(s) will only connect to network via LAN

What exactly happens when you try to connect via Wifi?

Do they detect the Wifi network at all?

Does Wifi show as red, orange or green in System Preferences->Network?

How is the connection set to work: DHCP?

Go to System Preferences->Network, select Wifi and post a screenshot.

I suppose that it also shows a GREEN dot, right?

This tells me that the Wifi connection to the router is ok.

Now, select Wifi on the left and click Advanced...

What do you see under:

DNS - do you see some numbers in grey or black? Grey means it is the DNS server automatically filled in by the router

Proxies - do you see anything checked? Usually, there should be no proxies set at all

Did you type these addresses in DNS yourself?

This seems likely to be the problem.

Make a note of these addresses, just in case you need them later (though I don't think you will).

Note that if you want to use them again, you have to type them exactly.

As a first try, simply delete them both, by selecting and clicking the "-" button.

What do you see? Does there appear some address in grey or not?

If you see something there in grey, click Ok, and then click Apply.

Is it now working?

The important thing is: does it work?

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