Service manager console can't connect to Service manager data warehouse SQL reporting services

Question

When I start Service manager console, it gives this kind of error:
The Service Manager data warehouse SQL Reporting Services server is currently unavailable. You will be unable to execute reports until this server is available. Please contact your system administrator. After the server becomes available please close your
console and re-open to view reports.
Also in EventViewer says:
cannot connect to SQL Reporting Services Server. Message= An unexpected error occured while connecting to SQL Reporting Services server: System.Net.WebException: The request failed with HTTP status 401: Unauthorized.
at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at Microsoft.EnterpriseManagement.Reporting.ReportingService.ReportingService2005.FindItems(String Folder, BooleanOperatorEnum BooleanOperator, SearchCondition[] Conditions)
at Microsoft.EnterpriseManagement.Reporting.EnterpriseReporting.FindItems(String searchPath, IList`1 criteria, Boolean And)
at Microsoft.EnterpriseManagement.Reporting.EnterpriseReporting.FindItems(String itemPath)
at Microsoft.EnterpriseManagement.Reporting.EnterpriseReporting.FindItem(String itemPath, ItemTypeEnum[] desiredTypes)
at Microsoft.EnterpriseManagement.Reporting.EnterpriseReporting.GetFolder(String path)
at Microsoft.EnterpriseManagement.Reporting.EnterpriseReportingGroup.Initialize()
at Microsoft.EnterpriseManagement.Reporting.ServiceManagerReportingGroup..ctor(DataWarehouseManagementGroup managementGroup, String reportingServerURL, String reportsFolderPath, NetworkCredential credentials)
at Microsoft.EnterpriseManagement.Reporting.ServiceManagerReportingGroup..ctor(DataWarehouseManagementGroup managementGroup, String reportingServerURL, String reportsFolderPath)
at Microsoft.EnterpriseManagement.UI.SdkDataAccess.ManagementGroupServerSession.TryConnectToReportingManagementGroup() Remediation = Please contact your Administrator.
We have a four server set-up where SCSM, SCDW, and sqls for both are on different servers. Also I have red that this could be a SPN problem, but this has  been worked on last week without the SPNs.

Answer 1

On the computer you get the "SQL Reporting Services server is currently unavailable" message please open the Internet Explorer and try to connect to the URL <a href="http:///reports">http://<NameOfReportingServer>/reports
This should open the reporting website in IE. If this isn't working you should check the proxy settings in IE. If the URL doesn't work in IE it won't work in the SCSM console as well (and vice versa).
Andreas Baumgarten | H&D International Group
Actually I can't access to the reporting website. It asks me credentials 3 times and then return a blank page. Also error message comes to the EventViewer System log with id 4 and source Security-Kerberos.
The Kerberos client received a KRB_AP_ERR_MODIFIED error from the server "accountname".
The target name used was HTTP/"reporting services fqn". This indicates that the target server failed to decrypt the ticket provided by the client.
This can occur when the target server principal name (SPN) is registered on an account other than the account the target service is using.
Ensure that the target SPN is only registered on the account used by the server.
This error can also happen if the target service account password is different than what is configured on the Kerberos Key Distribution Center for that target service.
Ensure that the service on the server and the KDC are both configured to use the same password.
If the server name is not fully qualified, and the target domain (domain.com) is different from the client domain (domain.com), check if there are identically named server accounts in these two domains,
or use the fully-qualified name to identify the server.
I can access the website directly from the server which hosts Reporting Services.
Also I query "setspn -Q HTTP/"reporting services fqn" whit result NO SUCH SPN FOUND.