# 72005: LiveSync MongoDB pipeline is invalid Identifier: `livesync_invalid_pipeline` A LiveSync MongoDB connector could not start because the aggregation pipeline in its configuration was not accepted by MongoDB, for example because it references a stage or field that is not allowed. ## What you should do Correct the aggregation pipeline in the [connector's configuration](https://ably.com/docs/livesync/mongodb.md). Check for unrecognized operators or invalid syntax, and make sure every stage is one MongoDB accepts on a change stream. ## Why it happens The MongoDB connector could not start because MongoDB rejected the aggregation pipeline in its configuration. This is usually an unrecognized stage or operator, a field that isn't allowed, or a syntax error. ## What you'll see The error is reported with code 72005 and HTTP status 400. The message is of the form `invalid pipeline: `.