The hosted NLTK data archive became flaky/403ing around 2024-11-25. The fix shipped in unstructured 0.16.11 (PR #3796): users confirmed upgrading to 0.16.11 resolved the 403. So update to 0.16.11 or newer and reinstall cleanly — one user needed a full reinstall before the fix took effect. If you are pinned to an older version, install the NLTK data manually with import nltk; nltk.download(...) for the needed resources so the downloader never runs.
Source: https://github.com/Unstructured-IO/unstructured/issues/3795
Source: https://github.com/Unstructured-IO/unstructured/issues/3795