Hello All. I am trying to log into the App store and I receive...An unexpected error occurred while signing in.
The data couldn’t be read because it isn’t in the correct format.
Any ideas on how to solve this issue?
[Re-Titled by Moderator]
MacBook Air 13″, macOS 10.15
Had this issue, the error message popped up while I was trying to update an App. I was prompted to sign in to the app store to verify and the unexpected error, data couldn't be read etc message appeared. I run Sierra 10.12.6 on a mid 2011 MacBook Air. I completed all the usual bits and pieces and eventually went into System preferences and logged out of my iCloud account and then logged back in. After this I was able to update and run apps without any problems. No more error message. Worked for me, may not work for others but worth a try.
Had this issue, the error message popped up while I was trying to update an App. I was prompted to sign in to the app store to verify and the unexpected error, data couldn't be read etc message appeared. I run Sierra 10.12.6 on a mid 2011 MacBook Air. I completed all the usual bits and pieces and eventually went into System preferences and logged out of my iCloud account and then logged back in. After this I was able to update and run apps without any problems. No more error message. Worked for me, may not work for others but worth a try.
In of the past 6-10 hours, affected macOS systems—including Sierra and High Sierra—can sign in to the App Store again, Apple has switched on access again. I’ve personally tested this, and it’s working
Do not consider this permanent though. Use this opportunity to:
This situation serves as a reminder: There are no guarantees of permanent access to legacy apps. Be proactive in seeking trusted alternatives or backup copies where possible to avoid being locked out in the future.
Spoke to Apple Support on this issue and the response is to the effect of 'your system is too old and unsupported anymore'.
A helpful developer has pointed out this - TN3138: Handling App Store receipt signing certificate changes | Apple Developer Documentation
At a guess, the App Store sign in request server response is encrypted in the new algorithm, the same one apps are now expected to handle, hence the The data couldn't be read because it isn't in the correct format.
As a result don't expect to be able to use your legitimately purchased software for an infinite period of time on a system Apple considers 'older' as it will be (now is) depreciated and you will lose access to those purchased apps and App Store access.
Same experience on a 2019 iMac with 10.14.6 (mojave). In my case, it followed a Disk Utility run to try to resolve a slowness issue. For example, the start page would take up to a minute to populate with the filled in icons. Before the Disk Utility run I did not have trouble signing in with Apple id.
I did not run a Disk Utility scan. I am able too get into the App store. I am trying to buy Space Gremlin and when I click on buy is when I get the message after trying to use the username and password.
Error 'An unexpected error occurred while signing in' when login into App Store
