No traces appear in LangSmith dashboard despite setting tracing env vars and running LangChain code (e.g., LLM invokes). May see no errors or intermittent 'failed to batch ingest' logs. Works locally but not in cloud/deployed, or vice versa.

Environment variables not correctly set, loaded too late (cached after first LangChain import), wrong casing ('True' vs 'true'), incorrect variable names (LANGSMITH_* vs LANGCHAIN_*), or missing restart after changes. No connection/batch ingest errors often indicate silent misconfig.[GitHub #216](https://github.com/langchain-ai/langsmith-sdk/issues/216)