NSURLErrorDomain -1012 on MacOSX 10.11

Have you installed something called "Avast?"

Please read this whole message before doing anything.

This procedure is a test, not a solution. Don’t be disappointed when you find that nothing has changed after you complete it.

Step 1

The purpose of this step is to determine whether the problem is localized to your user account.

Enable guest logins* and log in as Guest. Don't use the Safari-only “Guest User” login created by “Find My Mac.”

While logged in as Guest, you won’t have access to any of your documents or settings. Applications will behave as if you were running them for the first time. Don’t be alarmed by this behavior; it’s normal. If you need any passwords or other personal data in order to complete the test, memorize, print, or write them down before you begin.

Test while logged in as Guest. Same problem?

After testing, log out of the guest account and, in your own account, disable it if you wish. Any files you created in the guest account will be deleted automatically when you log out of it.

*Note: If you’ve activated “Find My Mac” or FileVault, then you can’t enable the Guest account. The “Guest User” login created by “Find My Mac” is not the same. Create a new account in which to test, and delete it, including its home folder, after testing.

Step 2

The purpose of this step is to determine whether the problem is caused by third-party system modifications that load automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.

Please take this step regardless of the results of Step 1.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in to the account with the problem.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of Steps 1 and 2.

I'm getting the same message while trying to install some updates. Never happened before.

Actually I had the same problem when checking the updates in the App Store. Error -1012 came up.

This happened after an upgrade from 10.6.8. to 10.11.4.

After browsing a while I came up with this solution which worked for me:

Open Safari and enter https://swscan.apple.com in the address field. The access the to web site is forbidden, but a green lock will appear. Click on the lock and display the certificates. There should be a hierarchy of 3 certificates.

Select each of the certificates. In the detail section, drag the certificate icon to the desktop. You will end up with 3 certificates on your desktop.

Now double click on each of the certificates on your desktop. Keychain Access will open (enter the administrator's password). Store the certificates in the 'System' section.

While in the keychain access app I also deleted all expired certificates. Not sure whether this is necessary, though.

Close the keychain access, fire up App Store again and - no error message anymore when checking for updates.

Hope this helps!

I cannot find the green lock, where should it appear?

What do I do if it works when I log in as a guest, but not when I am back in my own login? Problem remains…