In the latest update of Windows 10, push notifications must be approved via the Settings of the Windows machine. We recommend you to permit Windows notifications , so that you'll never miss a new conversation!
Setting up push notifications
The setting of push notifications in Windows 10 can be found via "All settings". This function can be found by clicking on the conversation icon in the bottom right of the start bar.
Navigate within "All settings" to "Systems" and then select "Notifications and actions".
Then, in the list of senders that can give notifications, make sure that notifications for both the browser and for web.trengo.eu are enabled (on). This way you're certain that notifications occur at the moment a new conversation is received!