If you have enabled desktop notifications from Gmail, but they are now showing, it might be that Chrome has disabled pop up windows for Gmail. 


To change this setting, we have to make an exception in Chrome:


1. Open Chrome settings

2. Select Show advanced settings...

3. From Security tab, select Content...

4. From popup windows, select Exceptions...

5. Add exception [*.]google.com and select Allow...

6. From here on, the popups will show on Google pages.


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