I've scoured the forums here for hours and can't find a way to fix this. I have around 400 audiobooks in M4B format, converted using AudioBookBuilder on a mac. I've never had any issues with these files, except with MP3tag.
With every.single.file I have tried, if I try to edit tags, I get the
[filename] cannot be opened for writing error.
If I pull these same files over to EZ Meta Tag Editor, change something about the meta and save it there, I am now able to edit the file in MP3Tag.
This is not a file ownership issue. I've used some of the tools (mp3val, foobar) that I've seen linked, but they either can't read M4B files or report no issues.
Any help is much appreciated.