Crystalreportviewer in VS 2013 - no parameter prompting

I have a VS 2013 VB Web Forms project using the Crystalreportviewer control. I use the control to call crystal.rpt files. If I call a .rpt file that doesn't have any parameters, the report runs and displays the data no problem. If I call a .rpt file that does have parameters, the report appears to run, I don't get prompted for parameters, and the control/report comes up blank. What am I doing wrong ???

Here's my code.

ASPX

<CR:CrystalReportSource ID="CrystalReportSource1" runat="server" EnableCaching="false"></CR:CrystalReportSource><CR:CrystalReportViewer 
        ID="CrystalReportViewer1" 
        runat="server" 
        AutoDataBind="true"  
        EnableDatabaseLogonPrompt="false" 
        EnableParameterPrompt="true" 
        HasRefreshButton="True"                             
        ReportSourceID="CrystalReportSource1" />

VB Code Behind

strReport = "C:\MyLocalPath\PeteTestReport.rpt"
CrystalReportViewer1.ReportSource = strReport
CrystalReportViewer1.RefreshReport()       

Note: I have already copied the 'crystalreportviews13' folder from C:\inetpub\wwwroot\asp_client folder to my application folder to fix the infamous BOBJ script error.

Thanks

Pete