I just upgraded to Yosemite, and I like the idea of using the Notifications Center, but for some reason when I get an email notification from any of my Gmail accounts, it appears for a few seconds and then disappears. This is for both the banner (which is the desired affect) and for the Notifications list. I would like for the email notification to remain in the list, at least until I check and/or acknowledge the notification. Has anyone else experienced this? Is there a solution? Thanks in advance. BTW, I've used this site for countless other problems I've encountered, but this seems to be the first one that I couldn't find the answer to without posting.