The most probable reason for the failure is that you built your application using the CE6 SDK (Toradex_CE600).
As CE6 does not support multicore operation, the function call is failing. Anyway, any application built with the CE6 SDK will only use one of the two T20 cores.
To overcome this, simply select the WEC7 SDK and rebuild your application.
If you need to stay with the CE6 SDK, for example to make the application compatible to CE6 and WEC7, there’s an API to activate WEC7 extensions during runtime of the application.