It is important that you have enabled bluetooth, internet and give the app permission to determine your location.
Bluetooth, location facilities and internet connection are important ingredients for a working app. Check if your WIFI and data settings are on a good connection.
Sometimes it is not possible to connect to the server for a while. This can be a temporary malfunction and is usually resolved within a few seconds. Always make sure you have a good internet connection. This can be better covered in some places than others. For example, are you in a garage or in a place with a lot of concrete? Then walk a bit away from the hub to check whether you can contact the server here
Always turn on your bluetooth and location facilities.