Why VSIX Extension and Toolbox Fails to Install extension in VS 2026?

We have an issue in Visual Studio 2026 were installing any Syncfusion VSIX extension and Toolbox extension for Visual Studio Toolbox configuration through the Syncfusion Installer during the installation of Essential Studio does not work as expected. However, you can manually configure them by following the steps below.

Steps to Manually Configure Syncfusion VSIX and Toolbox

Install Syncfusion controls in Visual Studio Toolbox:

1. Run the Assembly manager utility to install the assemblies into GAC. Refer to the below documentation to know about this.

   https://help.syncfusion.com/common/essential-studio/utilities#assembly-manager

2. Now, please run the toolbox utility to configure the controls in the Visual Studio toolbox. Follow the documentation given below for Toolbox configuration.

   https://help.syncfusion.com/common/essential-studio/utilities#toolbox-configuration

3. Open Visual Studio 2026 Toolbox and check whether toolbox control is configured after running the utility.

Note: To uninstall the Toolbox, Open Visual Studio 2026 and Navigate to Extensions -> Manage Extensions, Search for the “Syncfusion Toolbox Installer” VSExtension and uninstall if it is installed

Install Syncfusion Visual Studio extensions:

1. Open the command prompt as an administrator and navigate to the following location:

   **C:\Program Files (x86)\Syncfusion\Essential Studio\{Platform}\{Version}\Utilities\Extensions\VSIX Installer**
   

For example:

**“C:\Program Files (x86)\Syncfusion\Essential Studio\Windows\31.2.12\Utilities\Extensions\VSIX Installer”**

2. Run the SyncfusionVSIXInstallerConsole.exe with the following arguments based on the platform:

Arguments:

           /action:install /isinstaller:true /platform:"{Platform}"

For example:

           /action:install /isinstaller:true /platform:"WPF"

Please pass the arguments to the SyncfusionVSIXInstallerConsole.exe by referring to the table below, based on the platforms installed on your machine. This ensures the correct configuration for your environment.

3. Open Visual Studio 2026 and check whether the Syncfusion VSIX is configured properly after running the utility.

Note: To uninstall the syncfusion VSIX manually, Open the SyncfusionVSIXInstallerConsole.exe in command prompt as an administrator (refer the steps above) and the run below command.

Arguments:

           /action:uninstall /isinstaller:true /platform:"{Platform}"

For example:

           /action:uninstall /isinstaller:true /platform:"WPF"