Failed to load expression host assembly. Details: Could not load file or assembly or one of its dependencies. The system cannot find the file specified. (rsErrorLoadingExprHostAssembly)

Error:

Got the following error after upgrading SSRS.

Failed to load expression host assembly. Details: Could not load file xxxxxxx or assembly or one of its dependencies. The system cannot find the file specified. (rsErrorLoadingExprHostAssembly)

Fix:

For SQL Server 2014 to 2016, copy the missing dll to the new folder.

From…

C:\Program Files\Microsoft SQL Server\MSRS12.MSSQLSERVER\Reporting Services\ReportServer\bin

To…

C:\Program Files\Microsoft SQL Server\MSRS13.MSSQLSERVER\Reporting Services\ReportServer\bin

Sources:

https://social.msdn.microsoft.com/Forums/en-US/bf46213b-de66-4e32-80d7-e4c3135c5978/after-reinstalling-ssrs-got-error-failed-to-load-expression-host-assembly-details-could-not-load?forum=sqlreportingservices