Make sure the RabbitMQ server is up and ready to listen.

If the RabbitMQ server is in a docker container make sure the application container can communicate with the RabbitMQ container, also if you're using a docker compose file, keep in mind that RabbitMQ takes time to warm up even if you set the config "depends on" it'll still take time. if this is the case, try to run the RabbitMQ server separately make sure it is completely up and listening and see if the connection is established in the application.