Cannot access my books on Clip+

I bought a new Clip + to listen to audiobooks from the library.I downloaded three books using Overdrive, which I could then see and hear in my music direcory.

The second time I used it, it froze in the FM radio.To reset the Clip+, I held the on button down for more than 20-30 seconds. 

Now I can’t see any books on my device, yet when I look at the space utilization It is 1/3 used, so the books are probably still on the device, but I can’t access them.

In desperation, I tried to connect to my computer with the Clip+ off and holding the center button down.

No change, I cannot see the books even looking using my PC.

I’m not sure what’s going on, but you can clean up and erase the media content on your player through a Format of it under its Settings. 

Do note:  

When your player is connected to your computer under USB MSC mode (set under the player’s settings), your computer only sees the files that had been transferred to the player when the player was connected under MSC mode.  Likewise as to MTP mode.  Regardless, all the files show up and are playable on your player, under whatever USB mode setting.

Perhaps this is the explanation?