We always recommend you use the most up to date version of the app, and that your phone's operating system is up to date.
Make sure you check for any app updates by searching for "Macs Adventure" in Google Play or the App Store. Once you locate the app, see if it has an "update" option highlighted.
If the app is launching OK, but your navigation is not working, please check your phone's GPS is switched on, and that you have allowed the app permission to access your location. You can check this within your phone's settings.
The Macs Adventure app is currently supported on iOS 13.0 and higher / Android 5.0 and higher. The app is not supported for use on iPad or Android tablets.