Pesky "AMD-Action:authenticate:SP" and its Fix
OCTOBER 29, 2015

Over the last few weeks, I’ve been plagued with an issue within the OSX El Capitan App Store, that resulted in me being unable to install any updates or install/purchase new applications. At first, I wondered if this was due to my hasty upgrade to the GM of OSX 10.11, which almost certainly was going have a few bugs and issues being the initial release of a new OS.
After a few attempts at trying to fix the issue using Google, it seemed that although I wasn’t the only one being stung by this error message, it also wasn’t particularly wide spread. A recurring theme was the use of multiple Volumes on OSX, where the ‘/Users/’ directory was not where the App Store expected it to be.
I had an alert for some new updates that needed applying. I clicked the notification to find out that it was an update for iTunes & OSX 10.11.1. Excellent! Maybe a quick and easy fix for my problem. My first worry was that the update wouldn’t work as it was via the App Store (oh the irony!), however it sailed through and I rebooted my box.
I excitedly clicked the App Store icon, and hit ‘Update’ - no joy. Up popped “AMD-Action:authenticate:SP”.
Eventually, after a bit more googling and studying of other fixes, I managed to come up with the following fix:
Check where you user directory resides.

This can be checked by going to ‘Users & Groups’ in System Preferences, and right-clicking your user – you may need to click the lock at the bottom left of the window to allow access to the menu. From here, select ‘Advanced Options’ and look for the home directory.
Once you know this directory, it’s time to jump into Terminal and run some command line magic.
Symlink the correct Users directory to ‘/Users/’

1 cd /
2 sudo rm -rf /Users #Run this at your own risk!!
3 sudo mkdir /Users
4 sudo ditto -V /Volumes/Your HDD/Users/Shared /Users/Shared

What that final line does, it copies the files within the Shared directory in your user path, to the same directory in the root. Please remember to swap the first location to that of your user directory - tab completion may help here!
After doing all of this, I ran the App Store, and voila! Updates were once again working.