Getting error in Report Server while selecting an option "As User Viewing the report"

We are receiving the same error. Here is a capture from our log file:

library!ReportServer_0-19!f54!04/30/2019-08:30:16:: i INFO: Call to GetItemTypeAction(/Operations/Field Operations/CSR WorkBench). User: MFAOIL\Cynthia.St.Clair.

library!ReportServer_0-19!f54!04/30/2019-08:30:16:: i INFO: RenderForNewSession('/Operations/Field Operations/CSR WorkBench')

dataextension!ReportServer_0-19!f54!04/30/2019-08:30:16:: i INFO: Opening SqlConnection with ClientConnectionId 4e41de21af3b4ec8abece0909938556d

dataextension!ReportServer_0-19!1bf8!04/30/2019-08:30:16:: i INFO: Opening SqlConnection with ClientConnectionId c63c8c37765f47dc83918873f3f00f62

dataextension!ReportServer_0-19!10b4!04/30/2019-08:30:16:: i INFO: Opening SqlConnection with ClientConnectionId 9edcc92f55994d299ad2a8b7f2788403

dataextension!ReportServer_0-19!10b4!04/30/2019-08:30:16:: i INFO: Opening SqlConnection with ClientConnectionId 9edcc92f55994d299ad2a8b7f2788403

processing!ReportServer_0-19!174c!04/30/2019-08:30:16:: e ERROR: Throwing Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: , Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: Cannot create a connection to data source 'Landing'. ---> System.Data.SqlClient.SqlException: Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'.

   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling)

   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)

   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)

   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)

   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)

   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)

   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject