Notification popup isn't shown when there's an incoming conversation on your Windows workstation.
Go to your browser's notification settings: -Chrome: Settings > Privacy and security > Site settings > Permissions > Notifications -Edge: Settings > Cookies and Site permissions > Notifications -Firefox: Settings > Privacy & Settings > Permissions > Notifications
Enable notification sending.
Add Communication Panel URL as an allowed site.
Confirm your notification behaviour from Windows Settings > System > Notifications & actions.