I have a couple of old Stephen King audiobooks (read by the author) on cassette tape. Yesterday I used Audacity to digitize the first book and exported the files as AAC (m4a) then renamed them to m4b files and added them to iTunes. I had them added to iTunes Match and they show up on my iPhone 6s now but they won't play. The iPhone says the media format is not supported. They play fine in iTunes. I wanted to use the m4b format because, it's my understanding, that this format will enable me to pick up where I left off when I listen again later. Any tips on what I can do? Because i use iTunes Match I can't really sync my library directly to my computer.