Master Collection won't install- "Session UUID file exists - will not overwrite..."

Hello,

     I have a user with a 2013 iMac and a 2013 MacBook pro (both up to date in Sierra). Three weeks ago, I made a new package for 2017 CS Master Collection, since a lot of our users are on 2015 software and aren't able to update on their own. The MacBook Pro was able to download the 2017 package without any issues. The iMac keeps failing, using the same installer. The error I'm getting is- "PackageKit: Session UUID file exists - will not overwrite /var/folders/zz/zyxvpxvq6csfxvn_n0000000000000/C/PKInstallSandboxManager/91B7417A-01B1-4050-8816-311ED0D5419A.activeSandbox."

According to this Adobe article- 'Creative Cloud package "Installation Failed" error message', I need to repackage the installer because a certificate is invalid for some of the older software. However, I packaged this software AFTER the March 9th date that the article lists. And if the certificate is the issue I don't understand why it successfully installed on multiple computers, some of whom had older versions of Creative Suite and some of whom didn't. I'm willing to repackage the software and try that, but I'm not confident that will work.

Can I just download the .activeSandbox files in that folder? What are my next troubleshooting steps?