Apple Music can't find my files.

The "missing file" issue with exclamation marks happens if the file is no longer where iTunes or Music expects to find it. Possible causes are that you or some third party tool has moved, renamed or deleted the file, one of its parent folders, the drive it lives on has had a name change, or you've moved a non-portable library to a different path (see Make a split library portable for details). It is also possible that iTunes or Music have changed from expecting the files to be in the pre-iTunes 9 layout to post-iTunes 9 layout, or vice-versa, and so is looking in slightly the wrong place, or that you've been too aggressive when deleting duplicates at some point.

Select a track with an exclamation mark, use Cmd-I to get Song Info, then click No when asked to try to locate the track. Look on the file tab for the location the library thinks the file should be. Now take a look around your hard drives. Hopefully you can locate the track in question. If a section of your library has simply been moved, a folder renamed, or a drive label has changed, it should be possible to reverse the actions. If the difference between the two paths is an additional Music folder in one path then this is a layout issue. I can explain further if that is the case. If everything is where it is supposed to be try Repair security permissions for iTunes for Mac - Apple Community.

In some cases the library may be able to repair itself if you go through the same steps with Get Info, or when playing a track, but this time click Locate and browse to the lost track. It may then offer to attempt to automatically fix other broken links. Although it says something like "use the same location" I think it expects to find the tracks in the same artist & album layout they were in previously, with one systematic change to the path.

If you want me to try to provide specific advice please post back the following details:

1. The location of the media folder under iTunes|Music > Preferences > Advanced
2. The location of a sample missing track shown under Song Info > File > Location that begins file://
3. The true path to the file whose details you gave in 2

See also FixLinks - an AppleScript to repair broken links in Music - Apple Community.

tt2

The script is designed to work with a selection of items in the library. There is a section that starts -- calculate file extension which is where the .ext value is calculated. It depends on the track kind. Perhaps there is a kind I haven't catered for. If you look in the Songs view of the library and enable the Kind column what is the Kind of the track causing a problem?

tt2

I've updated the script to add in the two extensions, and also make it clearer if there is another extension that I've overlooked.

tt2

Hi, so the difference between 2. & 3. suggests to me that the track has been renamed to match the default <Media Folder>/Music/<Album Artist>/<Album>/## <Name>.<Ext> layout that iTunes uses, but somehow the new path hasn't been saved in the database. Not quite sure why you got that report from the script, but you could try again and see if, for this particular track, things work out better if you start the search from /Extreme SSD/iTunes/iTunes Media/Music/Glenn Underground/. Assuming it can repair tracks from that album we can investigate how to make the script find other tracks starting from a higher level folder so you can fix more at the same time.

tt2

Another alternative (depending on how important the attached track metadata is to you and if the files are referenced in static playlists -- the following process will lose that information) is to find all files marked with an exclamation mark, select them, delete the file (or remove download if they're referenced in an iCloud Music library) and then drag the locally stored files back onto the Apple Music app. The provisio here is that the link has to be a permanently broken one for this to be appropriate; as Turingtest2 noted, if your file was flagged as being unavailable as it was on a disconnected removable drive or network share when you tried to access it, remounting that drive and simply opening up the Info window for the track will force a relink. If there a group of files with the same issue, tapping "next" from the Info window will walk through them. It's boring to do, but is often the fastest and safest way to relink.

Unfortunately there's no built-in way to force the Apple Music app to look for a group of files moved to a different location or renamed in some way; you can only do it one-by-one.