Sorry I should have said iPhone.Are you sure? Are the files on your Mac but just not showing in iTunes? What actions did you take before their disappearance? If they are gone, you can restore them from your backup.
There is nothing. Just 1 album.Do you not see the music, or do you mean it's just in the cloud? If it's in the cloud, you tap the ellipsis and select Make Available Offline.
That's just it. I've been using AM and offline mode since day 1 with no problems then out of the blue it's just dumped everything.If you just started with Apple Music give it a day to sync everything. The missing music might be there tomorrow.
Cloud services have the problem that troubleshooting them is generally much harder. They are an application running on a server (and not just one server, a huge network of servers). You cannot restart that application, you cannot re-install that application, the application is modified potentially daily without you having any possibility to know which version is currently running, with changes you don't know about. Even resetting all user data isn't easily possible (what works is to create a new AppleID).That's just it. I've been using AM and offline mode since day 1 with no problems then out of the blue it's just dumped everything.
However, from my testing I have found that, at least on iPads, only the list of songs (and playlists) will be added back to the 'My Music' section but the actual music files will not be downloaded automatically.If you sign out of iTunes your offline music will be removed and will re-download when you sign back in. My guess is the one album still there was one you purchased.