The server was missing the specific assembly for the Microsoft Report Viewer Runtime. It was a common dependency for applications built on the .NET Framework of that era, but finding the exact installer for version 12.0.0.0 was like trying to find a specific snowflake in a blizzard. Most search results tried to redirect him to newer versions—14.0, 15.0—but the application was stubborn. It demanded its specific spirit animal: Version 12.
If you are a developer integrating this into a project, use these packages: Microsoft.ReportViewer.Runtime.Common Microsoft.ReportViewer.WebForms.v12 Microsoft.ReportViewer.WinForms.v12 2. Critical Prerequisites The runtime will often fail to install or run without the SQL Server System CLR Types Microsoft Support You must install the Microsoft System CLR Types for SQL Server 2014 .NET Framework 3.5 SP1 is enabled on the system. ⚠️ Lifecycle & Support Notice microsoft report viewer version 12.0.0.0 download