VisualStudio: no debug output

Also worth checking - right-click in the output window, and ensure "Program output" is checked.

There's an option under Tools-Options-Debugging-General, Redirect all Output Window text to the Immediate Window. Make sure that's disabled. However, by default it isn't, so I doubt that's your issue. You can also just check your Immediate Window to see if it's outputting there.

You might also want to try resetting all your environment settings. (Tools - Import and Export Settings - Reset all settings.)