onResume never called

This may be more of an Android question, but I'm using the standard generated Activity class so thought its worth an ask here.

I'm trying to pause my app when the user presses the home button or blanks the screen. I've overridden and defined the 'suspended' and 'resumed' functions in my Main.cpp and created a ChangeBroadcaster and Listeners so that I can 'pause' the two main threads in my app: a HighResolutionTimer, and the AudioDevice. 

I've got it to stop the timer and close the audio device when leaving the app, but found that when returning the app is still frozen and unresponsive, after a short time Android detects this and asks to close it. None of my log messages from the JUCE part show up for the 'resumed' action, and I also tried adding a log statement to the onResume function in the Activity, which also doesn't appear,  so looks like it never gets called at the Java level. 

Going to do some more investigation when time allows just wondered if anyone else had experienced this before.