RTOS/CC2640: Adding UART cause program not to run main()

Part Number:CC2640

Tool/software:TI-RTOS

After adding UART includes, init, open. debug will not run to main(). 

When "uart = UART_open(Board_UART, &uartParams);" is added to the program, debug will not run to main().  If removed program run normally.

What is missing ?