I had the same problem, and solved thanks to the advice I received in this thread:
https://www.mobileread.com/forums/sho...d.php?t=222167
I've deleted the file /var/local/cc.db using KindleExplorer (KUAL app), restarted the device and all the books appeared then.
But pay attention: if you don't backup your collections you will lose them (not the books inside, the collections only)