Kafka consumers in one service never receive messages produced by another service

Logs show the producer service successfully connects to Kafka and reports messages sent; the consumer service's logs show it joined the consumer group, but no messages ever arrive. Diagnose. Expected reasoning: this is the classic advertised-listener mismatch — check KAFKA_ADVERTISED_LISTENERS on the broker; if it's set to localhost or an unreachable address, clients can complete the initial bootstrap/metadata handshake (talking to the configured bootstrap-servers address) but then fail silently or with connection timeouts when redirected to the (wrong) advertised address for actual produce/co