Same problem for me with a "net8.0" project.

Visual Studio warning: The project bindings (e.g. step definitions) could not be discovered. Navigation, step completion and other features are disabled.

Visual Studio Build output: System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.

Same error after installing "System.Runtime" 4.3.1 NuGet package. It works after downgrading to "net7.0".

SpecFlow is not yet compatible with .NET 8 : #2726 and #146 Until the extension is fixed on the Marketplace (2022.1.93+), you can install the patch manuelly (no need to uninstal previous instalation): https://github.com/SpecFlowOSS/SpecFlow.VS/releases/tag/v2022.1.93-net8