I have been working on a project for two months. It was running so slow that I decided to do a Mac Clean (using a untility).
This morning, I opened FCPX to make a small change and it no longer brought up my external drive and project.
I took the drive to work to troubleshoot further. At work, the drive comes up but with permissions issues. I granted read/write access to specific folders and was able to open my Project storyline, but I have no idea how to open my event.
And this is at work. I want to be able to restore it at home since it's a personal project. Having looked up similar issues, I see that some say there's a DCIM or CONTENTS file...not here.
Can you post a screenshot of the root folders of your hard drive? It's possible even without a DCIM or CONTENTS folder that there's a folder confusing FCPX.
Secondly, if you did a clean install, it may be the permissions that are the problem. Did you repair permissions for your external drive? You may find that your (me) user has no permissions because those permissions were created on your previous (me) user and not transferred (this happens even if you use the same "name").
Get info on the drive itself, not just specific folders. Unlock the Sharing and Permissions (lock icon at bottom right). Add a new user (plus button). Give yourself read/write permissions. Then click the gear icon and make you the new owner of the drive. Then apply that setting to enclosed items (also in the gear menu).