Your device or computer could not be verified. Contact support for assistance.

I just followed these instructions and it worked perfectly. All 4 needed to be deleted. They get rebuilt when restarting. My new Mac with Sierra had been set up by my IT department using a LAN cable. No idea if that had any issue here but the WIFI could connect easily but there was no internet. Neither to the App Store nor Safari etc.

Thanks peterfromdanville

You can see the rather long solution description I posted on page 7 of this and it has worked for most people, but today I have to update it because I had updated to High Sierra from Sierra and my computer kept locking up with a black screen and I had to keep turning it off and restarting it (but that's another story), so I did a time machine restore to Sierra 10.12.6 and then I could log into my iCloud and iTunes but not into the App Store. After following my instructions here several times it still didn't work. I also deleted ALL files from Macintosh HD/Library/Preferences/SystemConfiguration (except com.apple.Boot.plist), emptied the trash and then, before restarting, follow charmole advice and go into iTunes and first de-authorize your computer, then restart. After you restart, the first thing... the very first thing you do (close any and all windows with error messages or anything that wants you to log in) and FIRST go to iTunes and authorize your computer. Then my App Store worked fine and so far, apparently, so does everything else.

Sorry for the double post. The first one didn't post everything I wrote, so I posted it again. Then I found you can edit your post but you can't delete it. You can see the rather long solution description I posted on page 7 of this and it has worked for most people, but today I have to update it because I had updated to High Sierra from Sierra and my computer kept locking up with a black screen and I had to keep turning it off and restarting it (but that's another story), so I did a time machine restore to Sierra 10.12.6 and then I could log into my iCloud and iTunes but not into the App Store. After following my instructions here several times it still didn't work. I also deleted ALL files from Macintosh HD/Library/Preferences/SystemConfiguration (except com.apple.Boot.plist), emptied the trash and then, before restarting, follow charmole advice and go into iTunes and first de-authorize your computer, then restart. After you restart, the first thing... the very first thing you do (close any and all windows with error messages or anything that wants you to log in) and FIRST go to iTunes and authorize your computer. Then my App Store worked fine and so far, apparently, so does everything else.

I’m going to summarize all the solutions that have worked on this apple support forum and put them into one “do-all-this” instruction. If you follow this to the letter, this should get you back into the App Store (and probably into iTunes Store if that’s your problem). At least one of these solutions have worked without doing all of them (deleting the network interface.plist), but it didn’t work for me, so if you do everything on this list, then restart your computer, there’s a 99% chance it will fix your problems. DON’T RESET YOUR PASSWORD OR CREATE ANOTHER ACCOUNT TO TRY TO BYPASS THIS PROBLEM.

1. Go to your hard drive (not your username) Library/Preferences/Systemconfiguration folder and delete EVERY plist in it except com.apple.Boot.plist. (this is all safe because all plists will be re-made when you restart your computer)

6. The FIRST thing you now have to do is open iTunes and go back to “store” or “accounts” and click on “authorizations” and authorize your computer. Now everything should work fine. Open the App Store and click on purchases. Sign in if it asks you to with your Apple ID. It should now work fine.

Try resetting your Apple ID

If that doesn't help, contact iTunes billing

Click: iTunes Store Account & Billing / Billing Inquiries / Email Us

In the future, if you have problems with your iPad, post in the

iPad forum. Click New / Discussion / Using iPad.

This is the Mac App Store forum for Mac OS X.

My app store randomly broke too. right in the middle of needing critical applications. apps that were long ago fully bought and paid for. No problem buying from iTunes, it's a glitch in App Store.

My app store is broken as well. It will not allow log on download programs or update anything currently installed. I've tried twice to contact Apple Support on this issue and they have miss guided and been otherwise useless. I too believe its a glitch with in App Store itself. I know my account information because I use it at work and log on everyday manually.

I'm having the same problem. Per tech support's suggestion, have tried re-downloading the 10.6.8 package and also repairing permissions. Still getting it. I can use my Apple ID and Password to log into iTunes; just won't work for Mac App Store.

According to the Rep I spoke with on Phone via 1-800-MY-APPLE

About this "authentication/verification/validation/etc" situation

Apple's Servers are so overloaded/swamped/maxed-out/etc they're having some problems

Imagine everyone try to get through door at same time as DoorMan try to check ID's - dig ?

Appears Lion is very popular

Try again later - all we can do

Mine went down a week ago and has not come up since. So it's not Lion here.

Had this problem, too. Seems to be an issue with network interfaces is checked by App Store. You can delete the plist-File for the network. Here´s a howto http://welcome2inter.net/news/newsdetails.html?identity=35

I got the same error message yesterday. It means that Apple's servers are blocked and they're not able to log anyone else in. This morning I was finally able to log on to the store, however, the download for Lion has been going on for more than 5 hours and not even half of it is downloaded!

I have the same problem. Everything works like a charm on my iPad.

On my iMac, however, the app store gives me the message "Your device or computer could not be verified. Contact support for assistance." Needless to say, supprt was not able to resolve the issue. If anyone has managed to resolve this issue please post.

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Ok - this *maybe* seems a solution, least appears to be working for me

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Created an entirely New Apple ID - New Password, etc - for App Store

This is in addition to the current one I still have with Apple (in general, used to get to this discussion)

And also use same one for iTunes, but ONLY at iTunes - is 'no go' for App Store

.

Which is to say - I now have 2 Apple ID's - one for Apple/iTunes and one for App Store

Yes, a pain in butt, but may be only solution until "something" gets fixed ?

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Also, in case it matters in the Grand Scheme of Things ....

I was one of those who got hacked last Summer/Fall in the Great China iTunes Hackfest

Yes, 1/2 my bad for not having a 'hard(er/est) password' - but that's now corrected

And Thank You Apple for restoring the $20.00 to my iTunes Account

Thought all issues/matters in that regard were now 'fixed' ?

Maybe not ? Least not regarding the App Store ?

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Again, YOU go create a new ID/Password - might 'work' for you too

Then perhaps you can get Lion

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This worked for me and I was having the same issue:

Solution

1) Delete the file Macintosh HD/Library/Preferences/SystemConfiguration/NetworkInterfaces.plist

2) Restart OSX

3) Try logging into Mac App Store again.

Hope this helps 🙂