Mac App Store Broken on macOS 10.14 and Earlier

That's the same experience I had using the app store in 10.13 and 10.14 a few years ago. I couldn't log in, and any attempt to download anything would be met with an inscrutable error. Based on these experiences I assumed it had been broken in those versions of macOS for a while.

This would also prevent those users from downloading installers for other versions of macOS.

I've had this for a while now running 10.14.6 Mojave. I'm not certain, but I believe it began before 27 January. I get the message about "data couldn't be read because it is in the wrong format," so I can't sign in, but I can install Mac App Store updates (did one last night).

@vintner links to download macOS installers outside the App Store are easily accessible. I downloaded them several months ago using OCLP. Mr Macintosh has them on his website, too.

I have several Macs running older macOS versions. Filling in a few gaps for the behaviour of App Store:

10.12.6 has the same symptoms as the Apple Support discussion: "An unexpected error occurred while signing in. The data couldn't be read because it isn't in the correct format."

10.11.6 has slightly different wording: "plist parsing error", which suggests it might be a data file compatibility issue rather than a certificate issue.

(I don't see much point testing earlier systems but if anyone cares I still have a Snow Leopard system running somewhere, and I may be able to locate one external drive on which I had every version installed from 10.6 up to 10.10.)

10.13.6 isn't showing buttons at the top so I can't see Purchased, Updates, etc. If I sign out and try to sign in it goes through the password and two-factor then still shows as not being signed in, but no error message.

10.14.6 I have one Mac still signed in, and it can download purchased apps, but I expect that will only last until the session expires. Booting from a clone of that system required sign-in and it fails with the same alert as 10.12.6.

10.15.7 is OK.

I pine for the old days before app stores existed. Thankfully I still rely on apps downloaded or purchased outside the App Store. But it sucks that a single point of unavailability conditions the installation of plenty of apps that still run on older Macs running previous Mac OS versions. I really hope this is just temporary.

@Bri Yes, this has happened several times over the years, and there was a long period where the CSS was broken, but as of early January, at least, it was working again.

@vintner Besides the links here and on Mr. Macintosh’s site, there are also two apps.

@NaOH That sounds like a different behavior than what I saw. Maybe there are two different problems.

@Riccardo Indeed!

The previous problems with older OS versions accessing Apple hosted resources, iTunes, the Mac App Store, iCloud.com, and CSS files served by Apple, were due to the security certificates included with the original OS installers having expired for those servers.

The fix was eventually to download an install a new CA2-G1 certificate from Apple PKI.

Might be worth it for folks experiencing this to check ou the certificte expiration dates in Keychain Access for Apple's server resources.

Looks like it's fixed this morning. I successfully signed in and installed a free app on my old Mini with 10.13, where I couldn't in the last few days.

Like Michel Fortin on 10.13, the issues seem to be resolved on Mojave 10.14.

Also works for me today after failing yesterday, and I've widen my tests.

App Store works including sign-in and re-download of purchases on fully updated 10.9.5 (Mavericks) thru 10.14.6 (Mojave), with one complication:

On 10.13.6 (High Sierra), App Store still has no buttons in its toolbar to let me switch between Featured, Top Charts, Categories, Purchased and Updates. The corresponding items in the Store menu are also missing. I see reports about this dating back to 2018-2020 so not a new problem but it appeared to only affect some people; perhaps server side as App Store gets much of what it displays from Apple's servers and that may include which buttons to show.

If there are system updates available, the Updates view can be accessed via a button in System Preferences > App Store, but it might be difficult or impossible to get to App updates with no system updates pending.

I was able to re-download some of my purchases on 10.13.6 by searching for them in the store, but this doesn't help for re-downloading purchases which are no longer listed (I confirmed using other OS versions that they were still downloadable from purchase history). One app failed to download via this method and ironically App Store told me to try again using the missing Purchased view.

As for older systems: App Store cannot establish a secure connection to the store on 10.6.8 (Snow Leopard), 10.7.5 (Lion) and 10.8.5 (Mountain Lion). The "continue anyway" option doesn't work. iTunes also fails to connect (same store infrastructure). On Mountain Lion this also makes it difficult to access the system updates since Mountain Lion is the version which moved them into App Store. I was able to use the softwareupdate tool in Terminal to install updates (except iTunes 12.4.3 which i had to install manually, probably because of another expired certificate).

I suspect the App Store and iTunes connection issue in 10.8.5 and earlier is a TLS version compatibility issue, because with 10.7.5 and 10.8.5 I saw the G2/G3 Apple root certificates appear after installing security updates, and they didn't help.

Followup re Mountain Lion and earlier: Wireshark confirms it is a TLS version problem. The server rejected the TLSv1 connection due to protocol version.

@David Thanks for testing.

App store still not working for me (as of Feb. 8) using Mojave 10.14.6 with sign-in error "data couldn't be read because it is in the wrong format." Can browse store but downloads and updates fail.

I ran into this over a week ago, attempting to launch Sound Studio, which had been running reliably for years with no issues. Asked to sign into the App Store, which promptly rejected my Sign in. manifested on both my older Classic Mac Pro (5,1) workstations running Mac OS High Sierra and Mojave. After two fruitless episodes with Apple Support, I threw up my hands and bought a new license from Felt Tip. I had a project to finish. I downloaded the app directly from their web site. I reasonably suspected Apple, as I could sign into my Apple ID account, iCloud, iTunes, the Music Store...

Yesterday, I found sign-in access had been restored on both machines, through no effort on My part. Apparently Apple quietly tweaked or fixed the App Store backstage.

Apple did this. Reminder: Upcoming Changes to the App Store Receipt Signing Intermediate Certificate. [https://developer.apple.com/news/?id=rzloycgp] They informed developers, but not a word to customers. It seems that Apple Support either did not know, or was not permitted to tell us.

All Apple support needed to say would have been – "Sit tight. We’re aware of the issue and are working on it.” – Just THAT. Grrr. Arrgh.

Cost me an un-needed software license, three working days and half a weekend putzing around trying various technical fixes to no avail, including re-installing MacOS High Sierra on Workstation #2. Pain. In. The. Arse.... At least I won’t have to buy a Mac $tudio.... This Week.

Just adding some thanks here to Michael Tsai for posting about this and that leading to a resolution. I appreciate the effort and ongoing diligence of this blog. Thank you.

Many thanks to David Empson for the tests.
I was racking my brains for days wondering what had happened. Until I came across this blog. Out of the blue on MacBook 7.1 OS MacOS High Sierra 10.13.6 + all system updates from the store, "data couldn't be read because it is in the wrong format" began to appear :(
High Sierra is the highest possible version of the operating system for my MacBook.
What I didn't do, and rolled back using Time Machine and reinstalled several times, nothing helped.
I dug up a bunch of forums on the Internet, wasting a lot of time and nerves.
Everything worked fine only if I installed it using the patcher Catalina 10.15 and higher.
At the moment (12.02.25 / 00:42 AM MSK) on High Sierra 10.13 the store application works, but the buttons Purchase / Updates / etc. are missing at the top :/
The programs I have already purchased, if I search by store, ask me to pay for them again :/

Does anybody know if they also reverted the change to SHA256 AppStore receipts back to SHA1 for old macOS versions?

@Hannes I don’t think so. It’s not that the receipts changed but that the old certificate expired and the new one is signed with SHA-256.

This is still broken on High Sierra 10.13.6 .. I sign in and it says I'm signed in, there is no logo in bottom left corner of App Store to view purchases; I did find a shortcut to "Purchases," but when I click it says I haven't downloaded any apps yet which isn't true. I'm just trying to make a bootable drive to reinstall High Sierra on my failed 2017 MacBook Air. This is a PITA. I also have a M1MBP -- I cannot download or open the High Sierra dmg file to create the bootable drive from there, either