You installed the x86 VSTO runtime but Office is 64-bit. Solution: Uninstall the x86 runtime and install the x64 version.
Install the Visual Studio Tools for Office Runtime Redistributable microsoft visual studio 2010 tools for office runtime -x64-
However, due to by Windows, if your add-in manifests are signed with SHA-1, Windows may block them. Update to SHA-256 certificates. You installed the x86 VSTO runtime but Office is 64-bit
Before installing the VSTO 2010 Runtime, ensure your system meets these criteria: Update to SHA-256 certificates
The Visual Studio Tools for Office (VSTO) Runtime is a set of components that allows Office applications like Word, Excel, PowerPoint, and Outlook to host the .NET Framework Common Language Runtime (CLR). This enables developers to create managed add-ins and document-level customizations that extend the functionality of the Office suite. The runtime includes two primary parts:
Basic command-line examples