REST Service Error: 503 Service Unavailable (Tenant Under Maintenance)

Description

This error occurs when a REST API call to a service receives an HTTP status code outside the 20x (success) range, indicating the request was not processed successfully.

The REST service returned a status code that is not 20x - i.e. not OK - Status code received: 503 Service Unavailable Response body: {"error": {"code": "Upgrade","message": "Tenant under maintenance. Maintenance type: Upgrade"}}

Error Details

• Status Code: 503 Service Unavailable
• Error Code: Upgrade
• Message: "Tenant under maintenance. Maintenance type: Upgrade"

Cause

The target tenant (commonly a Business Central or Dynamics 365 environment) is temporarily unavailable because it is undergoing a scheduled or in-progress upgrade. During this maintenance window, the tenant's API endpoints reject incoming requests to prevent data inconsistency.

Resolution

• Wait for the maintenance/upgrade to complete before retrying the request.
• Implement retry logic with exponential backoff for integration jobs that may run during maintenance windows.
• Check the tenant's admin center or service status page for an estimated maintenance completion time.
• If the issue persists beyond the expected maintenance window, contact the tenant administrator or platform support.