Otdfbt

I'm not sure if this is the right place for the question.

I got a Windows Server 2016 with IIS 10. We got an application developed on .net deployed here. The application uses the reporting service of another server on the same network through a report viewer.

<rsweb:ReportViewer id="rvwAnexoTransaccional" runat="server" InternalBorderColor="White"
 BorderColor="White" BackColor="White" ShowRefreshButton="False" ShowPromptAreaButton="False"
 ShowPrintButton="False" ShowParameterPrompts="False" Height="1903px" Width="1004px"
 ProcessingMode="Remote">
 </rsweb:ReportViewer>

On the .cs the report is updated this way:

System.Configuration.ConnectionStringSettingsCollection rootWebConfig = System.Web.Configuration.WebConfigurationManager.ConnectionStrings;
 string strCadenaCon = rootWebConfig["ReportServer"].ConnectionString.ToString();
 Uri reportUrl = new Uri(strCadenaCon.ToString());

 rvwAnexoTransaccional.ServerReport.ReportServerUrl = reportUrl;
 rvwAnexoTransaccional.ServerReport.ReportPath = new Parametros_BusinessLogic().ReportProject + "AnexoTransaccional";
 rvwAnexoTransaccional.ServerReport.SetParameters(parameters);
 rvwAnexoTransaccional.ServerReport.Refresh();

From the development server with the same specs we have no trouble. However on the production server, the same user that is configured to call this reporting service got his permissions removed from C: drive. The inetpub is on the D drive anyway and all the temp files from the app are on the D drive too. This wasn't a problem at first cause we use the reports on the apps for a while, but then we started to get the following error:

----------------------------------------
----------------------------------------
HandlingInstanceID: 29b0c977-b11a-4c81-9e3c-311e77c0af17
An exception of type 'System.Net.WebException' occurred and was caught.
-----------------------------------------------------------------------
05/22/2019 12:58:33
Type : System.Net.WebException, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Message : The remote server returned an error: (403) Forbidden.
Source : System
Help link : 
Status : ProtocolError
Response : System.Net.HttpWebResponse
Data : System.Collections.ListDictionaryInternal
TargetSite : System.IO.Stream GetRequestStream(System.Net.TransportContext ByRef)
HResult : -2146233079
Stack Trace : at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
 at System.Net.HttpWebRequest.GetRequestStream()
 at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
 at Microsoft.Reporting.WebForms.Internal.Soap.ReportingServices2005.Execution.ReportExecutionService.ListSecureMethods()
 at Microsoft.Reporting.WebForms.Internal.Soap.ReportingServices2005.Execution.RSExecutionConnection.GetSecureMethods()
 at Microsoft.Reporting.WebForms.Internal.Soap.ReportingServices2005.Execution.RSExecutionConnection.IsSecureMethod(String methodname)
 at Microsoft.Reporting.WebForms.Internal.Soap.ReportingServices2005.Execution.RSExecutionConnection.SetConnectionSSLForMethod(String methodname)
 at Microsoft.Reporting.WebForms.Internal.Soap.ReportingServices2005.Execution.RSExecutionConnection.ProxyMethodInvocation.Execute[TReturn](RSExecutionConnection connection, ProxyMethod`1 initialMethod, ProxyMethod`1 retryMethod)
 at Microsoft.Reporting.WebForms.ServerReport.EnsureExecutionSession()
 at Microsoft.Reporting.WebForms.ServerReport.SetParameters(IEnumerable`1 parameters)
 at Reportes_AuditoriaTransaccional.imbBuscar_Click(Object sender, ImageClickEventArgs e)
 at System.Web.UI.WebControls.ImageButton.OnClick(ImageClickEventArgs e)
 at System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument)
 at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Additional Info:

MachineName : USQASWSPC000160
TimeStamp : 22/5/2019 16:58:33
FullName : Microsoft.Practices.EnterpriseLibrary.ExceptionHandling, Version=3.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
AppDomainName : /LM/W3SVC/1/ROOT/SCF2-6-132029525861419819
ThreadIdentity : scfec
WindowsIdentity : IIS APPPOOLDefaultAppPool

This 403 error occurs only on the call to reporting service trough the reportViewer. We can access to the reporting service configuration, or by URL. Also the app is still working and we got access to the database server (where the reporting service is located). Also if we change the web.config (any change) or restart the IIS the reportViewer works again for a few request (Maybe 3 or 4 reports) and then we get the 403 forbidden error again.

Like I mentioned we don't have this issue on the development server that is using the same reporting service on the same server. So we can point out that is the User configuration, however I need to point out what files or permissions are required so they can give me enough permissions to.

What local files are accessed on the request to the reporting service? Am I looking for the right solution to this ?

Thanks for any help.