How are notifications meant to work?
With Roundcube 1.6.1, and a current Chrome (113.0.5672.93) on Windows, they don't seem to do anything useful. If I enable 'display browser notifications', and I have Roundcube in an undisplayed browser tab, then the notification only becomes visible when I switch to that tab. I then enabled both browser notifications and 'play sound', and switched to another tab to send a test email. After waiting for 15 minutes I still had no notification from the undisplayed Roundcube tab.
So, basically, the Roundcube tab must be visible for notifications to work, in which case i don't need notifications anyway.
This doesn't work at all for Firefox. I never get a notification, and have to manually refresh the page to see if there any new emails. I can set 'display desktop notifications' for Firefox (but not for Chrome), but this does nothing either.
Roundcube is set to check for messages every minute.
I just meet the same problem as you.