50% of books can't be downloaded

[phuongnd08]

Not sure why, but out of 10 books I'm trying to download, at least 50% of them is not going through. The tool reporting this error:

[20:08:26] ERROR    Error downloading “Playing to Win”: RetryError[<Future at 0x104f77fd0 state=finished raised CloudflareChallengeError>]   main.py:93

This happens with certain titles and not the others. For example, it works with "myths-of-strategy-en" but fails with "playing-to-win-en-ag-lafley-and-roger-l-martin"