TestExecute displays this message when your test cannot launch a tested application instance, because the number of currently running application instances equals or exceeds the number needed by the test.
The number of application instances that should be started by the test is specified in the Count column of the Tested Applications editor (in scripts, you can access this value through the TestedApps.AppName.Count property). If the number of currently running instances is equal to or greater than this value, the test engine does not launch new application instances and displays this message box to inform you about the problem.
This message box signals that the actual conditions differ from the expected conditions for the test run. This may affect the test execution and cause the test to fail.
To avoid the problem, before the test starts, make sure that the number of application instances matches the expected number. If you need no application instances running before the test starts, terminate the existing instances. You can do this by closing the application through its user interface or by terminating the application processes through Windows Task Manager.