Currently change streams are disabled when a CSFLE MonogClient() session is used.
This is due to this CSFLE specifications.

Mongocryptd will not support “collectionless” aggregation metadata sources, which read metadata that doesn’t pertain to a particular collection. The drivers should not contact mongocryptd for such commands, since they don’t have a particular schema to pass to mongocryptd, so it is the drivers’ ultimate responsibility to return an error to the application for the collectionless aggregation metadata sources:

    $currentOp
    $changeStream for watching a database or the whole cluster
    $listSessions
    $listLocalSessions

Enable auto decryption and change streams in the presence of auto-encryption-settings