To use MS SQL Server Reporting (SSRS) reports in a “Web Page” widget you need to add an option to the SSRS report URL to allow it to be embedded into another widget, i.e. IFRAME. The option is "Embed=true".

Example URL: https://servername/ReportServer/Pages/ReportViewer.aspx?FolderName/Reportname&rs:Command=Render&rs:Embed=true