The new "Heap and Stack Usage" view is aimed at baremetal (non-RTOS) applications.
From your screenshot, it appears that you are probably creating a FreeRTOS based application - can you confirm?
When debugging such an application, this will cause the "Heap and Stack Usage" view to be disabled. [ We are looking at making what has happened in such cases more obvious in a future release.]
If you are generating a FreeRTOS based app, then instead please take a look at the "FreeRTOS TAD" views that are available via the "FreeRTOS" menu of the IDE (and described in the IDE's FreeRTOS Debug Guide).
Regards,
MCUXpresso IDE Support