@GooglePlayMusic Just got a Chromebox. So if I want to upload music to GPM (and I do) I have to hit the Upload Music on the left-hand nav. No Music Manager like I had with Windows. I tried to upload 8 MP3s and all it said was "Uploaded 0 of 8..." They never uploaded.
Thanks for getting back to us – try the troubleshooting steps for uploading your music here: http://yt.be/help/28CE . Also, you can contact our support team for help here: http://yt.be/help/i16t . Hope this gets resolved!