Notifications not showing on Windows 7

[chilly2go]

I am using this great component in a private project and on my testing system everything works fine. Now my parents try to use the site and can't see the notifications.
All Systems are running Firefox 66. The only other difference I found is that I am running win10 and my parents still use win7.
The site I'm building for my parents is build on laravel 5.8 and is using the included setup using webpack to compile the assets.
Is there something I missed? Might I have done something wrong?