Android has a number of default settings to help optimize the battery. These settings can cause delays to applications in how fast they are allowed to wakeup from the background when getting a push notification. The default is to optimize battery performance which works in general for most apps that are not time sensitive. For a calling application, the battery optimization will cause delays before your phone will start ringing and should be turned off.
Depending on your phone manufacturer, the battery optimization settings may be in different places. To turn off battery optimization, go to Settings, then locate the menu for "Apps", though in some Android versions it might be "Apps&Notifications" and locate the officeXtend or nCommand Plus application. Your settings might show a "See all xx apps" header. Touch the text to expand the list to see all apps if the list is not already expanded, then scroll down until you find the app you are using.
For Samsung and other models, touch the Battery section, then choose unrestricted as the battery optimization method. This should update the optimization settings for Samsung.
For other device manufacturers, you might have to to expand the Advanced section and touch the Battery option. A section might be titled "Battery optimization". If this section says "Optimizing battery use", then you may experience delays when ringing. To fix this, touch the "Battery Optimization" section. This will bring you to a list of apps. The default is to show apps that are currently "Not optimized". Touch the header that says "Not optimized" and choose "All apps" from the options. This will expand the list to show all apps including ones that are currently being optimized. Scroll down the list until you locate either officeXtend or nCommand Plus (whichever app you're using). Touch the app title and then choose "Don't optimize" from the choices and choose Done to save the selection.
