My MacBook Air lost ethernet connectivity

In reading all the posts. I think it's software related. Two things to try. In recovery run disk utilities to repair drive. Then boot to safe mode and test you internet. Safe mode cleans cache files and disables some third party programs.

Start up your Mac in safe mode - Apple Support

Also in system preferences network. Click on ethernet, then advanced, then TCP/IP and renew DHCP lease.

Dang!?

Do other USB things work in that port?

To find out if it's system wide or user specific, try this...

Open System Preferences>Users & Groups, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.

Does it work in the new account?

Make a New Location, Using network locations in Mac OS X ...

System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.

System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.

The interface that connects to the Internet should be dragged to the top of the list.

Sys Prefs>Network>highlight the Interface you're using>Advanced>TCP/IP>Configure IPv4: Using DHCP.

If using Wifi, instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.

System Preferences>Network>choose interface>Advanced>Proxies Tab, make sure none are set, like for HTTP & HTTPS.

System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...

8.8.8.8

8.8.4.4

1.1.1.1

9.9.9.9

Apply.

You have some corrupt or missing files that affect ethernet and wifi. Or you have a program that is blocking it. Can you remember any programs you added or changed since it was working? Are you using any cleaning software or antivirus software. or VPN. I thought about having you download and run Etrecheck, which runs a diagnoses of your system. But to do it , you would have to drag and drop the app from the external drive to the internal. Then when it ran, save the report and then drag and drop it back to the desktop of the external drive so you could post it in here.

https://etrecheck.com/ Up to you if you want to try it.

Here is a terminal command that will list your internet connections. network setup -listnetworkserviceorder

Won't do anything but will show network order and if on.

Are you using the same usb connection on the MacBook every time. Or have you tried different ones. I note that your MacBook Air originally came with a thunderbolt to ethernet adapter. Do you have one? When you get a (cable not connected) and you know the adapter works, then it would be the connection on the MacBook Air. Which may sometimes loose power. Usually doing the Nvram or SMC reset fixes it or just a restart. Do Nvram for 4 chimes. Going to about this Mac systems report and checking under usb with it plugged in will tell you if the computer sees it. If your adapter and ethernet cable will work on your wife's computer, then it's not the adapter or cable. As far as WIFI. If the keychain password for WIFI is different than what you are typing in, it will get rejected. You could check keychain to see. The password will be under systems or icloud( your router name). You right click -get info-check show password box- enter user password. Or go into router and check WIFI password and name. And also, as in the case of the new drive. You have to make sure that when you join, that you get the setting right. It should be WPA2 or WPA2 personal. You can check this in router settings. Whatever your router is set to is what must be interned in when joining a network.

Hi, see if this cures it...

Have you done a PRAM reset, CMD+Option+p+r...

Reset NVRAM or PRAM on your Mac - Apple Support

In fact, do 3 in a row, takes a bit of time.

Intel-based Macs: Resetting the System Management Controller (SMC)...

http://support.apple.com/kb/HT3964

I still think it's a software problem. To check if this is the case. All you need to do is boot to your internal drive to recovery. You should show and have WIFI in the upper left corner. To check, click on and open Safari in recovery. Then click on a link and see if it loads. You can even test the ethernet By closing Safari. Going to the top left for WIFI and turn it off. Pug in your USB adapter and do the same thing that you just did to test WIFI. If both work then the problem is software. When done, don't forget to turn the WIFI back on.

Since your external drive, when used to boot your computer allows you to have internet. I still think it's a software problem. You could try a reinstall thru recovery to see if it would fix any files that are corrupt. This will not delete any personal files. The way passwords work to WIFI is that it would be the name of your WIFI source and password. Which would be the router. To change the the name of the internet you would have to do it in the router WIFI configuration as well. That is why it would not accept your password. When joining a new network you need to put in the password and name you use for the router. What BDAqua was tell you to do was manually change the settings for internet not the name or password. If trying to use WIFI. Go to the WIFI Icon and click on it then join other networks then then show networks. If you see your network click on it and join. If it asks for a password and or WPA2 WPA2 Personal WPA2-PSK. Put it in.

Did you ever recheck in network, to see if you could add ethernet back in your internal drive? By clicking on the + and then clicking on interface to see if it's there. I would suggest two things A Nvram reset and a SMC reset. Nvram is Command Option P R keys and power button. Allow three chimes. SMC reset is Shift Control Option and power button for 10 seconds. I remember that I had an old Macbook that the airport card was going out. And I would loose WIFI. It would show as on, but no connection. I would have to turn it off and then back on. This worked till it finally stoped working. Running a hardware test would not show any fault for WIFI. I ended up with a USB WIFI adapter.

Sorry to hear that. Go to your wIFI icon and turn off WIFI if it's on. Then go to system preferences Security & privacy, click the lock. Enter your password and go to Firewall and disable it. Renew DHCP lease. In network click the gear icon and make sure you usb ethernet is at the top of the list. Restart. Under network advanced TCP/IP and DNS your router IP should be showing.

It is only your Macbook Air that has this problem? No other devises in you home have any WIFI problems? Next time your WIFI signal drops, boot to recovery and try using the online help thru safari in recovery. If you do not have WIFI in recovery then your problem is most likely a hardware problem. Either the Airport card you got is faulty or the Wifi antenna if faulty. If you do have Wifi in recovery then something in the software is the problem. Some routers allow you to set a permanent fixed ip for your computer. So you can't drop contact when your WIFI is running. In network preferences, advanced,TCP/IP. Your IPV4 address is your computer address on the router. You would need the MAC address as well. Which can be found in advance, hardware.