The application was released earlier this week and was working for Windows Phone users before errors started to display. The Verge understands that Google simply revoked the API key Microsoft was attempting to use as the software giant had reverse-engineered YouTube's ad code. Microsoft's re-released app appears to have taken Google by surprise, despite the promise of a collaborative effort to build a Windows Phone YouTube application.
The Verge has reached out to Microsoft for comment, and we'll update you accordingly.
Update: Microsoft says it's working on resolving the issue with its updated YouTube app. "Google is blocking our updated YouTube app for Windows Phone," says a Microsoft spokesperson. "We are working with them to resolve the issue."