'The controller for path '/favicon.ico' was not found...' error

Finally resolved the issue. We had to make two changes:

• We're using OWIN-MixedAuth, and part of the issue was on the IIS Express settings (under "Development Server" section):

  1. Highlight the project in Visual Studio
  2. Open the 'Properties' panel on the right (or press F4)
  3. Set 'Windows Authentication' to 'Enabled'
  4. Set 'Anonymous Authentication' to 'Enabled'

• Another part of the issue: a corrupted applicationhost.config file used by IIS Express:

  1. Ensure you're showing hidden files in Windows Explorer.
  2. Go to the root of your project via Windows Explorer.
  3. Open the hidden .vs folder.
  4. Go to config > applicationhost.config, make a backup, and open it in Notepad (Notepad++ is better).
  5. Compare it to a working applicationhost.config file from one of our machines. We found lots of old sites that were listed in the config file which were not being used anymore.
  6. Once cleaned up, launched the app and it worked.