Microsoft ended Extended Support for the VSTO 2010 Runtime on July 14, 2020 .
The is a essential software component that enables Microsoft Office applications—such as Excel, Word, and Outlook—to run solutions built with Visual Studio. It acts as a bridge between the .NET Framework and Office, allowing custom add-ins and document-level customizations to function correctly. Key Features and Purpose vsto 2010 runtime
The VSTO 2010 runtime is 32-bit only internally. On 64-bit Office, it runs under WOW64. Microsoft ended Extended Support for the VSTO 2010