You might try this fix.
Fix IconStreams and PastIconsStream Registry Subkeys Corruption
If your computer is not affected by group policy , then the possible root cause for the Clock, Volume, Power and Network system tray icons to go into hiding, missing and disappearing from notification area is invalid or corrupted registry key entries of IconStreams and PastIconsStream. Microsoft KB945011 explains that “when the system or an application wants to put an icon in the notification area, the system or the application sends a discrete communication message to the operating system shell. If the operating system is very busy, that message may expire, or may time out. When this time-out occurs (such as shutdown prematurely), the icon does not appear in the notification area.” However, the error can happens more frequently than the cause specified by Microsoft.
To make the icons reappear, and enable the check boxes for the system icons, delete the specific registry keys.
* Run Registry Editor (RegEdit.exe).
* Navigate to the following registry key:
* In the right Details pane, delete the IconStreams registry entry.
* In the right Details pane, click the PastIconsStream registry entry.
* Exit Registry Editor.
* Restart the Explorer.exe process.
If the above does not work then you might have to try this.
All-in-One Registry Solution to Fix and Show Notification Are System Icons Disabled Issue
The following registry file contains all fixes listed above, and when apply, will delete all policies to disable the system icons, and reset and restore the notification tray icon streams to clean state.