My upgrade from Yosemite to El Capitan on my 2015 13" MBP kept failing for unknown reasons, so I did a clean install of El Capitan, which meant reinstalling everything else from scratch. In my iTunes preferences, I selected the iTunes Media folder on my external media drive, where all my content is stored. When I open iTunes, it shows all my music as being in iCloud and downloadable (I subscribe to iTunes Match and Apple Music), as opposed to already having been downloaded and available immediately. None of the MP4 videos I'd previously imported to my library are showing up, either -- only video content I purchased from the iTunes Store. All of my MP4 videos are still in the iTunes Media\Movies folder (in the case of my home videos) or in iTunes Media\[Artist]\Unknown Album (in the case of music videos). Is there some setting I've neglected to make? I did a search, and the result from an Apple Support page said to try using one of my previous iTunes Library.itl files. I did, and it had no effect. Do I need to re-import everything to my iTunes Library?