At the end of this post will be a link so you can see first hand what I am talking about.

I have an external Passport drive.  I have three absolutely identical projects in terms of frame rate, color space, etc.  I  open up Project 1; Media Creation recognizes the hard drive.  I open up Project 2, also recognizes the hard drvie.  I open up Project 3, and IT IS GRAYED OUT!!!  And now comes the wild part... I open Project 1 BACK up, and Media Creation drive is GRAYED OUT!!!!  WTF is happening???  Can ANYONE out there explain to me what is going on?  How can it recognize a drive once, and then when reopening the same project with no changes, it DOESN'T recognize it!

I am completely baffled.

https://www.youtube.com/watch?v=LVEjUDP5PKM&feature=youtu.be

I can't help you but I do believe you. I thought that this error occured only with G-Raid drives but I've seen it with a USB3 portable drive. Sometimes (rarely), I can link to files on a drive (so MC can see it) but I cannot render or transcode to it. Not a problem with disk permissions. Very intermittent.

What's on that external drive?  Are there multiple partitions or only one?  What's the format?  Is it HFS+ or perhaps Ex-FAT or NTFS?  Is your media in the Avid MediaFiles folder or is it AMA Linked?

Short guess is that once Media Composer gets a notion that the Volume is not going to work that applies to any other project opened until you quit and start up again.  You can try Refresh Media Directories to see if that helps, but what's on your external drive and how it's formatted are necessary clues to explain what's going on.

I am having the same issues.  10.11.6 and Avid 8.63  properlly formatted OSX drives

tried new user

reset mcstate and settings

reset AMA settings in shared users

reset users

usb3 drive... very similar to problem in this tread and another thread http://community.avid.com/forums/t/179512.aspx

Sure the drive hasn't gone to sleep? If restarting the system helps that might be the culprit.

Not in the case I have encountered. I can link to files on the drive so it is awake. Just don't see it in the Media Tool or rendering choices.

Does resetting the PRAM letting it chime 3 times help?

Although I'm quite sad about your situation, I'm also happy that finally I'm finding someone with the same problem!

I'm having the exact same weird behaviour with mostly our SNS EVO connected shared drives. Did you have any luck finding a solution for this problem?

I tried all of the suggestions above.

Please let me know if there's any more information. Going quite crazy here!

-Bas

running 8.9.1 on 10.12.6 but the problem occured on previous MC/macOS versions as well. On multiple machines :(

I've seen this and here is how i resolved this.

CLick on "go" on the top menu and then click on "Go to folder", then type /volumes/

You now see volumes mounted on your computer. Select the drives that's missing on MC and then unmount them. Remount the drives, they will now show up in MC