The system tray icons and clock disappearing is a reported problem in the optional preview KB5089573 update released at the end of May and the June KB5094126 update.
Check in the Update History section in the Settings app to see if either of those udpates have been installed.
Also, some people indicate if they have the WindHawk utility or some other utility installed to customize the start menu and taskbar, it seems there is a conflict with the utility and those updates.