This tray icon update problem, that you describe, is a
known bug in PopMan since version 1.1, when the tray icon feature was introduced.
I experience the problem about 3 times a year. It seems PopMan loses the connection to the tray icon and is therefore unable to update it in any way. You have to restart PopMan to make the icon work again.
Because the problem occurs so seldom, it's extra hard to track it down. It is much easier to eliminate a crash, where you have an address to start from, or a bug that can be reproduced.
Maybe, anyone with programming experience can take a look at the PopMan source file "TrayIcon.cpp" to see if there is something that I have overlooked.
Please report any further occurence of this problem here...