SSRS is not running.
View the event logs for further information. A service can stop for many reasons, including:
The service was stopped by an administrator
The service was prevented from starting because the user account could not be authenticated.
The service encountered an exception that stopped the service.
The service was improperly configured, which prevented it from starting.
Try to restart the service manually and review events for additional details.
You can attempt to restart the service by doing the following:
1. Open a remote desktop connection to the server that generated the alert.
2. Run services.msc
3. Right click on the "SQL Server (MSSQLSERVER) " and click "Start".