My mail app has stopped showing me the latest email.
Recently Apple Care did some changes to my iMac 21.5. The very next email I received in my Mail app only made the chime sound, and did not show me the actual email as it has been doing since purchasing this computer. How do I get back the ability to see the newest email coming in. Typically the new email shows in the upper right corner of my iMac screen. I am using MacOS Sierra 10.12.3, and the Mail app is 10.2. I liked being able to see the new email immediately without changing the screen I am viewing. Please help. Please understand, I am not referring to not being able to see recent emails within the Mail app. I'm speaking of - when I am in Safari or Pages and a new email comes into the inbox within the Mail app, the popup showing that email used to appear on my desktop. It no longer does this. I just hear the chime informing me something has happened.
iMac (21.5-inch, Late 2013), macOS Sierra (10.12)