Kurviger App - Map Style - Empty


I am using the Kurviger 2.2.20 Android 10 (api29) Huawei STK-L21
After downloading the map Dutch - Open Map Style -
Can’t choose anything
I Come back to the map of The Netherlands
Does anyone know a solution?
Thank You
Steven Brandsma

To open offline maps, use the menu “Open maps”,
then select the map file to open.

Map styles are different, they are used for rendering maps,
you can read more about them: