title: Visual Studio code F# won't run - "Starting client failed"
body: <p>I cannot for the life of me get F# to run in Visual Studio Code. I've had it up and running previously, but not with the most recent versions of the software.</p>
  <p>I installed the most recent versions of .NET and VS code a month ago and again now, did full deletes and re-installs both times (including deleting user/.vscode and roaming/Code manually), but the error persists.</p>
  <p>I am on a Windows 10 and have installed x64 versions of .NET Core 3.1 and VS Code 1.48 with the only extensions C# 1.23 and Ionide-fsharp 4.16. I have enabled Use Sdk Scripts for ionide, but otherwise run on default configuration. dotnet fsi is executed without problems in the command line.</p>
  <p>Looking at the VSC extension host log:</p>
  <pre><code>[2020-08-15 11:24:35.431] [exthost] [error] Error: Language client is not ready yet
      at LanguageClient.sendRequest (c:\Users\Bruger\.vscode\extensions\ionide.ionide-fsharp-4.16.0\fsharp.js:7887:19)
      at __exports.compilerLocation (c:\Users\Bruger\.vscode\extensions\ionide.ionide-fsharp-4.16.0\fsharp.js:4290:19)
      at fsacConfig (c:\Users\Bruger\.vscode\extensions\ionide.ionide-fsharp-4.16.0\fsharp.js:4730:12)
      at c:\Users\Bruger\.vscode\extensions\ionide.ionide-fsharp-4.16.0\fsharp.js:4797:20
      at Object.__exports.msbuild (c:\Users\Bruger\.vscode\extensions\ionide.ionide-fsharp-4.16.0\fsharp.js:4802:10)
      at activate (c:\Users\Bruger\.vscode\extensions\ionide.ionide-fsharp-4.16.0\fsharp.js:19152:91)
      at c:\Users\Bruger\.vscode\extensions\ionide.ionide-fsharp-4.16.0\fsharp.js:25116:90
  </code></pre>
  <p>which I believe is caused by this problem seen in the VSC F# log:</p>
  <pre><code>[Error - 11.24.35] Starting client failed
  Launching server using command Invalid macro definition. failed.
  </code></pre>
  <p>I'm stuck here as I don't know what macro definition this refers to or how to get more information about the failure.</p>