if you don't see anything with 1 collection and just a few (1 to 5) books, then I would try reinstalling the python libraries
if that does not help, you should next run it from a ssh console command. I have the command to run in the link below. that should make it very clear what the error is. As I mentioned earlier, it's almost impossible to debug it via the user interface.
https://www.mobileread.com/forums/sh...92#post4381692