title: Xamarin android references not found
body: <p>I am trying to open an existing xamarin project for android, and all the references have exclamation marks.</p>
  <p>The properties of the project are to compile for Android 9.0 sdk and this is set to automatically download and install.</p>
  <p>I get hundreds of errors and even get 'The type or namespace name 'System' could not be found'</p>
  <p>I already looked around on the internet and the only accepted solution was to reinstall windows/visual studio.
  Surely this cannot be right.</p>
  <p>Thanks for any insights.</p>