I have been stuck on this problem on and off for several weeks now. When trying to view a report using the perspective report viewer component, sometimes I get the error message “Enter a valid report in the "source" property in the Property Editor to display the report.” The report normally runs just fine the first time it is loaded on the page, but any subsequent requests tend to fail. My source property is bound to a report path, but I can get the same issue when using a static source.
For a bit more context, this report has some pretty nasty and complex data. I believed I had the problem fixed by using a custom cached query function. This has since not fixed the problem. The data in particular that is nasty is downtime reasons for each shift over a date range. I am pulling in my data to the report using a script data source because there is quite a lot of massaging of data that needs to happen to get the data from the database to the report.
I have also added extensive logging and don’t see any errors in my logs when the report viewer breaks. I did notice that under the reports section, the reports can get stuck “Generating Report” and “Fetching Report.”