Failed to instantiate the default view controller for UIMainStoryboardFile 'Main' - perhaps the designated entry point is not set?

Check Is Initial View Controller in the Attributes Inspector.

So this also happened to me too. I checked 50 times and my "Is Initial View Controller" was checked, believe me. It happened out of the blue. So how did I fix it?

1. Create a new Storyboard in your project, name it something like Main_iPhoneV2 (or iPadV2 depending on your original storyboard style)
2. Open the broken storyboard, click anywhere in the white area and press command-a, then command-c (select all and copy)
3. Open your new storyboard and press command-v to paste the same exact setup
4. Go to your project settings, change your "Main Interface" to the new Main_iPhoneV2 (If it's your iPad and you're writing a universal app, you'll have to edit the -Info.plist and look for the value "Main storyboard file base name (iPad)
5. Recompile, and stop pulling your hair out

First click on the View Controller in the right hand side Utilities bar. Next select the Attributes Inspector and make sure that under the View Controller section the 'Is Initial View Controller' checkbox is checked!