Windows 10 notifications in corporate environments | 1809 and above

Try this:
Computer Configuration – Administrative Templates – Windows Components – Windows Security – Notifications – Hide all notifications

If it doesn’t work, try this:
HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Windows\Explorer\[DWORD DisableNotificationCenter = 1]

For older versions check this:

https://blogs.technet.microsoft.com/platforms_lync_cloud/2017/05/05/disabling-windows-10-action-center-notifications/