I am encountering an error when clicking the ‘Run’ button in Power BI Report Builder

Hi Anonymous ,

I found there is a thread discussing a similar issue to yours. I hope the solution provided there can assist you in resolving your problem.

Solved: August release - Failed to load expression host as... - Microsoft Fabric Community

Ensure that the assembly bindings in your configuration files are correct. You can find these files at:

• C:\Program Files\Microsoft Power BI Report Server\PBIRS\ReportServer\web.config
• C:\Program Files\Microsoft Power BI Report Server\PBIRS\ReportServer\bin\ReportingServicesService.exe.config

Look for the assemblyBinding section and verify that the oldVersion and newVersion values are correctly set for Microsoft.ReportingServices.ProcessingCore and other related assemblies

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If the previous solution does not resolve your issue, could you please provide the following information for further troubleshooting?

• Does the issue occur when you run a different RDL file in Report Builder?
• What data source are you using in your RDL file?
• If your report contains any custom expressions, please ensure there are no syntax errors or unsupported functions.
• What version of Report Builder are you using? 

Best Regards