commerce client error 500

Go step by step and test.

1. System Preferences > iCloud

    Sign out and Sign back in. Test

2. Delete  com.apple.appstore.plist, com.apple.commerce.plist and test.

        Backup first.Quit all applications.

        Activate Finder by clicking on an empty spot on the Desktop.

        Hold the “Option” key down.

        Click "Go" menu in the Finder menu bar and choose Library from the dropdown.

        Click open Preferences folder. Scroll down the list.

        Right click on the

        1.  com.apple.appstore.plist and choose "Move to Trash”      

        2.  com.apple.commerce.plist and choose Move to Trash”.

        Close the window and restart the Mac. Test.

KaKaotalk.... doesn't work.....

What doesn't work?

I have the same problem, I did the procedure and error persists

KakaoTalk

It is a free messaging app mostly used in S.Korea.

Thank you. I learned something. I thought the person I was replying to was referring to your first post.

Do a backup, preferably 2 backups on 2 separate drives.

Quit the application.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J.  When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder.  Select Library. Then go to Preferences/com.apple.appstore.plist and com.apple.appstore.commerce.plist.  Move the .plists to your desktop.

Restart the computer, open the application, and test. If it works okay, delete the plists from the desktop.

If the application is the same, return the .plists to where you got it from, overwriting the newer one.

Thanks to leonie for some information contained in this.