Intellisense已停止为我工作，每当我运行VSCode时，OmniSharp日志中就会出现此错误。

[warn]: OmniSharp.MSBuild.ProjectManager
        Failed to load project file '/Users/leogaunt/Documents/Programming/Unity/Cube Stack/Assembly-CSharp.csproj'.
/Users/leogaunt/Documents/Programming/Unity/Cube Stack/Assembly-CSharp.csproj
/Users/leogaunt/.vscode/extensions/ms-dotnettools.csharp-1.23.1/.omnisharp/1.37.0/omnisharp/.msbuild/Current/Bin/microsoft.Common.CurrentVersion.targets(1178,5): Error: The reference assemblies for .NETFramework,Version=v4.7.1 were not found. To resolve this,install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application. You can download .NET Framework Developer Packs at https://aka.ms/msbuild/developerpacks

[fail]: OmniSharp.MSBuild.ProjectManager
        Attempted to update project that is not loaded: /Users/leogaunt/Documents/Programming/Unity/Cube Stack/Assembly-CSharp.csproj

我尝试重新安装该插件，并重新安装VSCode，但是它没有用。

我知道我已经安装了.NET Core，因为我是Mac用户，所以知道这一点，因为当我在终端中输入dotnet --version时，它会输出：

3.1.401

我正在Unity中编程，并且正在为iOS创建游戏。