Scripts no longer reloading/recompiling assets or scripts

Unity has suddenly stopped recognizing that any files have changed and is no longer compiling or detecting compile errors automatically. It is also not picking up art assets changes and reimporting assets.

The only way I can get Unity to recognize file changes is by clicking "Assets > Sync Mono Develop Project". Adding/deleting a file also seems to work, but I image this is for the same reason; Unity is synchronizing the project.

I have tried this with numerous projects, including completely empty new projects with a single script. I have restarted my computer multiple times, and even uninstalled unity and re-installed it. I've made changes using multiple editors (mono develop, visual studio, and notepad). It happens for both C# and javascript.

I'm nearly at my wit's end now. Does anyone have an idea what might be wrong here? I've done quite a bit of googling on this already but haven't turned up anything that helps.

 

In case someone else has this problem, here's what it was:

I somehow unchecked "Auto Refresh" in my Unity Preferences. I didn't even know this option existed, but having it unchecked was the entire issue.

Live and learn...