As described here the backend call is invoked only when submitChanges statement is reached. Check if the payload has the data.
Attach success and error callbacks as shown and put breakpoint in both functions and analyse or post the result here.
reqParams.success = this.SuccessHandlerFunction;
reqParams.error = this.ErrorHandlerFunction;
(you may also need to bind the context of controller via bind statement for further processing)
BR.