Android Question Reading Whatsapp messages

[prokli]

I found two solutions how to listen for messages via Whatsapp. Both are working perfect on my Samsung device (Android 9.0).
Whatsapp spy
and
NotificationListener library (NotificationListenerService) | B4X Programming Forum

Unfortunately both do not run on a low cost smartphone running Android 8.0.1
Pressing the button "Enable to Spy" (001.jpg) the device shows the message "This feature is not availabe on this device". (002.jpg)
But sending Whatsapp messages to this device shows a notification on the top of screen.

Any idea??