A practical checklist for missing dependencies, wrong paths, and environment mismatches in build and runtime errors.
Module not found errors often mean a dependency was never installed, the import path is wrong, the file moved, or the runtime environment differs from the one where the module exists.
Verify the dependency really exists in the current environment and that the import path matches the actual file or package name.
If the issue happens only in one environment, compare install steps, working directories, and build outputs across environments.
Do not assume the package is missing globally if the problem is just an incorrect import path.
Do not keep reinstalling dependencies without checking whether the resolver points at the right place.