In the past weeks I have seen several notebooks (including my own) that stopped working because they had imported the three library without a version identifier, thus defaulting to the latest release.
Three.js is moving fast and breaking things, but here’s what you can do:
-
For new notebooks: Visit @tom’s Module Require Debugger to fetch the require statement, complete with version identifier (although just
require("three@VERSION")works as well). -
For broken notebooks:
- Open your notebook’s version history and check the date of the latest change.
- Head over to the three.js page on npm and click the “Versions” tab, then hover over the version ages to find the latest version before your last change.
- Add the version to your require statement.
Happy coding! 
Edit: You may also want to check the Migration Guide for individual releases.