I have tried numerous times to expand the notification, but it doesn't work. I have used Android phones for years now, and am quite familiar with how the notifications work. I have included a screen capture showing examples of how the various notifications are displayed. I hope it helps.
The first notification is from the gmail app, and it is expanded, though of course with no "mark as read" button. The second notification is from Aquamail and is for the same gmail account. Note that it is not expanded, and I have tried many times. The third notification is from Aquamail for an exchange account. It is expanded and shows the "mark read" button, something which I use almost everytime.
As for the possibility of my gmail account having unread messages, there are none. I even checked directly with my gmail account online. In fact, I always mark every email I receive as "read" - it's one of pet peeves to not leave "unread" emails in my inbox.
As I mentioned in an earlier post, the problem began with Android 5.0.1, sometime in mid-April, I believe. I have a Samsung S4 from ATT.
Is the expanded notification working for other phones with a gmail acccount in Aquamail?
Thanks again.