[Users] Popup notifications not working

[Removed GDPR]

Hi,

Recently I opened a bug report about this but as Paul explained it
works for him:

http://www.thewildbeast.co.uk/claws-mail/bugzilla/show_bug.cgi?id=3963

Unfortunately I am unable to find the cause why it doesn't work for me.
Can someone please help me to find the reason and hopefully fix it?

In case this matters this is on openSUSE Leap 42.3, KDE Plasma desktop
(using kdm).

-- 
George