I checked it and found that,
In android 7.1.1 webweiw is replaced by chrome view.
Our app is currently works on webview.
In order to make app run on Android 7.1.1 you need to download web view from play store and enable it to use instead of chrome view which is by default.
Sorry at this situation we can not make any changes in it as the OS of 7.1.1 works slight differently. so changes need to be done on your end.
In future we will change the design of app and will adapt the new tech.
Thanks for writing us!