Welcome to devices that seem to go out of their way to block users.
Once upon a time there was a plugin called Kindle Collections and it worked great up thru K4 (you could configure it to what Calibre column to use to control your collection members)
Then the big A made changes, that prevented access to the devices data on newer models.
The PI still works with Calibre 5.x,
if you have an antique model.