SSRS server not available 503 error

For an SSRS instance that was working and now returns HTTP 503, focus on service state, database connectivity, and configuration.

1. Verify SSRS service and Windows logs

• On the SSRS server, open Services and confirm that SQL Server Reporting Services (MSSQLSERVER or named instance) is running.
• If it is stopped or repeatedly stopping, check Windows Event Viewer → System for Service Control Manager errors similar to Event ID 7031 indicating the SSRS service terminated unexpectedly. This pattern matches the scenario described where ReportingServicesService.exe crashes and causes HTTP 503.

2. Apply the relevant cumulative update / hotfix

• For SQL Server 2008 R2, a known issue causes HTTP 503 and SSRS service crashes when executing reports; the fix is included starting with Cumulative Update 3 and in all later builds.
• For SQL Server 2016, a known issue after upgrading SSRS to 2016 causes HTTP 503 when opening the web portal; the fix is in Cumulative Update 1 for SQL Server 2016 and later cumulative updates.
• Install the latest cumulative update for the SSRS version in use so that all known HTTP 503-related fixes are applied.

3. Confirm ReportServer database connectivity and credentials

• Open Reporting Services Configuration Manager and connect to the instance.
• Go to Database and verify the ReportServer and ReportServerTempDB databases are reachable.
• Use Change Credentials, re-enter the existing service account or SQL login, apply the settings, and restart the SSRS service. This step re-establishes the secure connection to the ReportServer database if credentials or security context were disrupted.

4. Validate URL configuration and bindings

• In Reporting Services Configuration Manager, check Web Service URL and Web Portal URL:
  • Ensure the URL reservations exist and match the host and port being used (for example, http://ctpu-374/ReportServer).
  • If TLS/SSL or host headers were changed, remove URL reservations and TLS bindings in the order documented (remove URL reservations, then TLS bindings, then recreate URLs and bindings) and test again.

5. Check clustered/remote SQL Server scenarios

• If the ReportServer databases are on a virtual SQL Server in a Microsoft Cluster Services (MSCS) cluster and the SSRS service account is NetworkService or another account that relies on the <domain>\\<computer_name>$ login, ensure that login exists and has access to the ReportServer databases. Otherwise, use an explicit domain account or SQL login for the report server database connection.

After these steps, if the SSRS service remains stable (no repeated crashes in Event Viewer) and the ReportServer database connection is valid, the HTTP 503 error should be resolved and the http://ctpu-374/ReportServer URL should become accessible again.

References:

• KB3171040 - "HTTP 503: Service unavailable" error when you open the SSRS web portal after you upgrade to SSRS 2016
• KB2285517 - FIX: "HTTP 503: Service unavailable" error message when you execute a report in SQL Server 2008 R2
• Troubleshoot server and database connection problems with Reporting Services
• Configure a URL (Report Server Configuration Manager)
• Reporting Services failing over - Microsoft Q&A