iMovie "Missing File" after moving library to external drive

Well, it seems quite possible that you are onto something with the suggestion to check the drive formatting. I admittedly do not well-understand all of the minutiae of disc formatting. However, when I went into Disc Utility, I discovered that there is sort of a “hierarchy” associated with that disc - sort of similar to folders and sub-folders (I think!) And the “sub-folder” was indeed formatted as APFS, but the ‘root” drive was something else (I’ve already forgotten details.) The actual disc was one I picked up used to replace an older disc that had recently died, and when I installed the “new” disc, it did not occur to me that I had to format the “root” drive.

I used Disc Utility and reformatted the “root” drive using Apple MacOS formatting. I’m now copying the iMovie library back onto that drive, a multiple-hour operation with my machine. When that’s done, I’ll re-check permissions and see if iMovie will find and open from the “updated” external drive. I’ll post results later, thanks again!

Solved! I forgot to mention earlier. I was talking to another Apple user friend about this, he had a similar problem with a 3rd party app (Lightroom) and discovered that he had to go into settings, then sharing, and “share files”. I tried that and it worked for me. Thanks for all of your help and suggestions!

After literally hours of moving the library file off the external drive, reformatting, returning the library file, double-checking permissions, etc., etc., I can open iMovie from the library file icon on the external drive, but attempting to open from the iMovie icon in LaunchPad still shows the “permissions error” pop-up.

At least I can open iMovie from the external drive and get on with my projects. Enuf time spent trying to sort out the ambiguities of iMovie itself. Thanks for all of the suggestions and support!

Marty

I appreciate the reply and suggestion, thanks! Disk Utility tells me that the external drive is formatted AFPS (case sensitive) - is that the same as AFPS? I'm not intimately familiar with nuances of all the formatting options.

APFS - indeed! Guess I’m getting a bit dyslexic in my older years. I was aware what “case sensitive” means, I just wasn’t sure if adding that constraint might be part of my problem. Thanks for the link to the explanation. I’ll be doing some exploring to see if that slight detail is part of the problem.

I'll give that a try and get back to you, thanks!

EDIT: When I looked, that "ignore ownership" is already checked.