Übertragung Fehlerhaft
It means that message was not accepted by the server, or there was problem with connection.
is the app working with android 8.X bzw EMUI 8.X
I have the same problem on a Samsung S8 and a Nokia 5, both with android 8.x. I started on an internal network. Its workin on the demo site.
Sorry about my bad english.
after change samsung to huawai p20 my client dosnt send any info. message "übertragung fehlerhaft".