We have a split e-reader family. I have a Kindle and my wife has a nook. Apprentice Alf has helped us to use purchased books on both devices.

The Glowlgiht 4 is giving me an odd problem. My wife told me the only books she's seeing on the nook are her B&N purchased content and of the sideloaded books.

So I plug it into Mac, load Calibre, and it shows all this content is loaded. I unplug the nook and there is no content.

I then plug it in, and sync over a book. When I unplug it, all the sideloaded books show up.

I plug it back in the Mac, confirm all the books are there with calibre, unplug it, and all the sideloaded books are gone.

Repeat the process, sync over one book and all the sideloaded books come back.

And all the sideloaded books have all their bookmarks, go straight to the last read page. None of the metadata is lost.

I feel like I should report this to nook support. But when I have reported issues with sideloading to them before and they almost always blow it off and won't open an incident.
There's two posibilities I can think of:

1. The file type needs to be set to All Types instead of Books or My Files or
2. You have a corrupt database. I had that on the Glowlight 3. Books would get scrambled and seemingly disappear. It was a mess I was never able to correct.

1. I want them to show up under books. There used to be a way to do that.
2. I assume if the database is corrupt, I can just wipe the device and sync all the content back over.

I'm not a big fan of the nook for sideloading. Both theKobo and the Kindle handle sideloading a lot better.

I think I may have to gift my wife a Kobo for Christmas and get her off the nook.