If the MQ for MQTT API is called successfully, ResponseCode=200 is returned to the MQTT client. If the call fails, error codes and descriptions are returned. You can find a solution based on the following error messages.

Table 1. Error codes
Error code Symptom and cause Solution
ONS_SYSTEM_ERROR The backend of MQ is abnormal. Contact Alibaba Cloud Customer Services by submitting a ticket.
ONS_SERVICE_UNSUPPORTED The call is not currently supported in the corresponding region. Contact Alibaba Cloud Customer Services to check whether the operation is available.
ONS_INVOKE_ERROR API call failed. Contact Alibaba Cloud Customer Services.
BIZ_FIELD_CHECK_INVALID Parameter verification failed. Check whether the parameters are valid based on the API reference.
BIZ_TOPIC_NOT_FOUND The topic cannot be found. Check whether the entered topic is valid or available.
BIZ_SUBSCRIPTION_NOT_FOUND The target subscription group ID cannot be found. Check whether the group ID exists or whether the filter is correct.
BIZ_PUBLISHER_EXISTED The specified group ID already exists. Try again with a new group ID.
BIZ_SUBSCRIPTION_EXISTED The specified group ID already exists. Try again with a new group ID.
BIZ_CONSUMER_NOT_ONLINE The client with the specified group ID is offline. Ensure that the consumer client exists and then try again.
BIZ_NO_MESSAGE No message matches the filter. Check the filter and check whether messages have been published in the query range.
BIZ_REGION_NOT_FOUND The region where you request the service cannot be found. Check whether the parameters for the region where you request the service are valid.
BIZ_TOPIC_EXISTED The specified topic already exists. Try again with a new topic name.
BIZ_PUBLISH_INFO_NOT_FOUND The requested group ID cannot be found. Check whether the group ID exists or whether the request condition is correct.
EMPOWER_EXIST_ERROR The current authorization already exists. Verify the request parameters and try again or query the authorization.
EMPOWER_OWNER_CHECK_ERROR The current user is not the owner of the topic to be authorized. Check the ownership of the resource.