Cannot solve issue with file corruption. Help!

Hello, I have been working on solving a file corruption issue (in both Articulate Storyline 3 and Articulate 360) that leads to the message "This project is invalid or corrupt and cannot be opened. It may have been created in an earlier version of storyline." To date, I have tried all of the following trouble shooting solutions:

• Made sure all minimum tech specs for software were met (they are)
• Going into "appdata" file and renaming from .tmp to .story
• Uninstalled with UAC off, installed latest version (of AS3) from Articulate site and restarted before testing
• Minimized file name and saved to the C: drive (C:\Articulate\[myfile])
• Confirmed that .NET Framework 4.7 was selected
• Even logged in a different user to make sure it wasn't profile related
• Had 2 different internal IS people check my trouble shooting

Frankly, I'm baffled. Everything works great until I close a file and try to reopen it. Then it's back to "invalid and corrupt" city. I'm working on Windows 10. I've shared files with support, and they've confirmed they're corrupt. The last ticket I had open was Case #02132016. The support person has been great, but nothing has solved the issue. Not even switching over to the trial of Articulate 360. I've attached the test file I created just today through the trial and got the same corruption message.