DA14683: How to troubleshoot what is blocking extended sleep modes?

Hardware: 

Custom board using DA14683

SDK: 

1.0.14.1081 (last updated in 2018, despite what the new renesas download link says)

Situation:

The DA14683 won't go into extended sleep mode.  

I issue the "pm_set_sleep_mode(pm_mode_extended_sleep);" command but the sleep state does not change.  The power consumption does not change.  From what I can tell it never changes the sleep state.

Questions:

1) How should I go about troubleshooting what is keeping the sleep mode from running?  How can I determine what is keeping the code from going into sleep mode?

2) Can you debug the sleep mode operation?