Cannot retrieve debugging output in Qt Creator
This problem can show up if more than one instance of Qt Creator is active. To fix the issue, simply close all the other instances of Qt Creator and it should work.
For me, I solved the problem by simply closing the running application built with the other qt creator. So not necessary to close the other qt creator.
Or you may be running a version of DebugView from Sysinternals, that causes the same result.