If you notice that your ScaledObject is in Ready=False, it could mean that the HPA is not generated successfully. Look at the pod description and you might see:
Status:
Authentications Types: quesumer
Conditions:
Message: failed to ensure HPA is correctly created for ScaledObject: error parsing RabbitMQ metadata: error parsing RabbitMQ metadata: missing required parameter "host" in [triggerMetadata authParams resolvedEnv]
Reason: ScaledObjectCheckFailed
Status: False
Type: Ready