I noticed that you've opened a support ticket on the same topic. So, let me post my answer here as well:
"In order to give a helpful answer, I will need more information about the current scenario and in what type of application the InstanceReportSource is used. If it is an application that employs the REST service, then InstanceReportSource can be used on the server - i.e. where the REST Service is working. Usually, such code is written in the ReportsController that resolves the report source. If the current web application is an ASP.NET app, where the processing is done server-side, then this problem should not occur.
I assume you are using a ReportProcessor instance to render the report in PDF format, but from the provided screenshot it is not clear when and how the report rendering happens. I can only see that the parameter in the report definition corresponds by name and value type to the parameters in ReportSource collection. You could inspect the RenderingResult.Errors array and check the inner exception details - it can give some clue what's wrong.
Please help us understand the current scenario by providing a runnable sample of the application so we can investigate it on our side and give a useful answer."
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