Harald wroteAre you using Unity 2019.3.12?
I am using Unity 2019.3.12f1
However, for some reason when I opened my scripts in Visual Studio today the errors no longer display. Very strange. I have no idea what would have changed between today and yesterday to cause this change. I had very recently upgraded from Visual Studio 2017 to Visual Studio 2019. Maybe just restarting my computer was all that was needed for the update to recognize the Spine directive... or something.