SqlBulCopy.WriteToServer(DataTable) results in System.Data.SqlClient.SqlException (0x80131904)

As part of a annual process, there is a need to insert millions of records to DB. I use SqlBulkCopy.WriteToServer method to do so.

When processing even a less number of records it encounter below exception.

System.Data.SqlClient.SqlException (0x80131904): A severe error occurred on the current command. The results, if any, should be discarded. A severe error occurred on the current command. The results, if any, should be discarded. The statement has been terminated. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlBulkCopy.RunParser(Bulk

Below is the code related:

utlConnection utlCoreDBConnection = HelperFunction.GetDBConnectionProperties("core");
string astrCoreDBConnection = utlCoreDBConnection.istrConnectionString;

SqlBulkCopy lSqlBulCopy = new SqlBulkCopy(astrCoreDBConnection);
lSqlBulCopy.BulkCopyTimeout = 0;
lSqlBulCopy.WriteToServer(ldtbActuarialActiveDetail);

Connectionstring from appsettings:

<connection ID="core" QueryType="SqlServerClient">
<dbstring value="Data Source=my-server;Initial Catalog=my-db;User ID=user;password=devpwd;TimeOut=1044;Persist Security Info=True;Asynchronous Processing=True"/>
<dbfactory value="System.Data.SqlClient" />
<dbnextquery value="select next value for sequence_name from sgs_system_management" />
<dbprevquery value="select previous value for sequence_name from sgs_system_management" />
<dbkeyquery value="select ident_current('name_of_the_table')" />
</connection>

Can anyone assist me with this exception?