I’m a new user to eM, January 2017 version 7 windows 7and I’m having problems SEEING if there is new mail as should be indicated on the taskbar with an envelope icon atop your eM Client icon
I am using Windows 10 and having the same problem. Mine has shown a white envelope only twice since i started using this program, even though I get new emails daily. Interestingly, just now I deleted the new emails that came in (there was no envelope for them, not black or white) and only then the envelope showed up. Maybe that was for one of the other email addresses on my account but it should have registered on the ones already there.
The envelope icon appears only for new unread messages. Could it possibly be that you e.g. checked your inbox through webmail or some other device? These messages would then not be registered by eM Client as new unread messages, only as unread messages and the icon would not be shown for them.