Check the tracking settings to see whether the app is tracking by distance or time.
To check your tracking settings, click the Okappy icon. Click More and then click Tracking settings.
If the app is tracking by distance you will need to move in order for the app to send its location.  If by time, check the time interval.  If this is set to 5 for example, then the app won’t send a location until 5 minutes has past.

ios tracking settings

Give the device a few minutes to send a new location then update the refresh the radar screen.  Are the device locations now showing?  If not, click Next