On Windows 10, the ShowBalloonTip method of NotifyIcon NEVER shows the balloon tip. This would appear to have something to do with Windows itself.
If I go to Settings > System > Notifications & actions > and find my running app (vshost32.exe in debug mode) and click on it, then turn on Show notifications in the action center, I can clearly see the balloon tip messages being added to the notifications, but never a balloon tip.
I assume this is a problem with Windows 10.
My NotifyIcon is VISIBLE
my_icon.ShowBalloonTip("Title", "Message", BalloonIcon.Info);
Found the problem - was simple: Quiet Hours was turned on in the notification center and this was preventing the balloon tips.
On my computer with Windows 10 version 1803, go to Settings > System > Notifications & actions, and turn on "Get notifications from apps and other senders". The ballontips from my WPF app will show up.
来源：https://stackoverflow.com/questions/42444541/showballoontip-not-working