You may have tried uploading something that wasn't a lossless file. You could correct that in the playlist that you're trying to upload.That has come up before and we'll probably make a change for it. Do you have cover art stored as folder.jpg?
Sorry for the delay Jim. All are FLACs. But I have had some 24 bit ones rejected, which was annoying, but then I just removed them.
As far as cover art, some are folder.jpg, a few are Cover.jpg, some are [Artist] - [Album].jpg, some are [Album].jpg. But the large majority of it is in the cover art folder as specified in MC.
Realistically, if my local MC sees cover art, then the upload should just pick it up and send it. I mean that even for stuff using the rules of Series and Season.