Usually when I have Maxi Sys Pro sitting idle I tap the home button on bottom tray, then tap open app page symbol in tray , and close out all the open apps including Diagnostic App by swiping the Apps off to the side.
  When I tap the power button and take the Maxi Sys Pro out of  sleep mode and tap the Maxi Sys App on the Home Screen it sometimes shows a message You are exiting diagnostic program and it doesn't open and I have to tap on the App symbol in bottom tray then tap on the Maxi Sys symbol there and then the page opens. Weird.