1. If you actually meant MSE keeps disappearing from SYSTEM TRAY area, then try this.....
Right click at an open spot of taskbar > select Properties > at Notification Area heading, click Customize... > scroll to find MSE > click the pointer at far right and select Show Icon and Notifications.
2. Another suggestion :
Right click at taskbar > select Task Manager > click Processes tab at top > find MSE > click it > bottom right, click End Process > click Applications at top > bottom right, click New Task... > enter the MSE into the Open box > then click OK.
Note : I don't use MSE anymore, so I don't know if it is listed as mse.exe in Task Manager Processes list. When you are at New Task option, make sure you enter exactly the same...