How to show Crystal report for two tables related by foreign key?

It looks like you are following the answer provided here https://qawithexperts.com/questions/138/how-to-show-only-a-single-record-with-crystal-report-in-aspn

Which looks ok to me & I don't think it is related to multiple table's data fetch but according to error mentioned by you in the image "Database Logon Failed" you need to provide database details while generating reports also, here is the example about how to generate reports with dynamic logon

            ReportDocument cryRpt = new ReportDocument();
            TableLogOnInfos crtableLogoninfos = new TableLogOnInfos();
            TableLogOnInfo crtableLogoninfo = new TableLogOnInfo();
            ConnectionInfo crConnectionInfo = new ConnectionInfo();
            Tables CrTables ;

            cryRpt.Load("PUT CRYSTAL REPORT PATH HERE\CrystalReport1.rpt");

            crConnectionInfo.ServerName = "YOUR SERVER NAME";
            crConnectionInfo.DatabaseName = "YOUR DATABASE NAME";
            crConnectionInfo.UserID = "YOUR DATABASE USERNAME";
            crConnectionInfo.Password = "YOUR DATABASE PASSWORD";

            CrTables = cryRpt.Database.Tables ;
            foreach (CrystalDecisions.CrystalReports.Engine.Table CrTable in CrTables)
            {
                crtableLogoninfo = CrTable.LogOnInfo;
                crtableLogoninfo.ConnectionInfo = crConnectionInfo;
                CrTable.ApplyLogOnInfo(crtableLogoninfo);
            }

            crystalReportViewer1.ReportSource = cryRpt;
            crystalReportViewer1.Refresh(); 

http://csharp.net-informations.com/crystal-reports/csharp-crystal-reports-dynamic-login.htm

There is another complete tutorial on this https://www.aspdotnet-suresh.com/2012/01/crystal-reports-sample-in-aspnet.html

If that doesn't help you, check similar issue's

https://community.ivanti.com/thread/31347

Also, as per the answer here https://www.experts-exchange.com/questions/28520468/Database-logon-failed-when-exporting-Crystal-Report-to-PDF.html you need to have SQL native client installed.