Hi,
It can be because of webhui configurationd in the backend,
1.Go to Tcode SICF
2.Go to service sap > bc >gui >sap > its > webgui
3.Copy the service and paste it in a new folder ex: sap > bc >gui > sap> its >test >webgui
4.Double click on the service
5.There you can find create/change service screen.
6.In that screen you can find the GUI Configuration button click that button.In that you have to set parameter.
7.There you have to set parameter as ~WEBGUI_SIMPLE_TOOLBAR and a specified value(for values find the step 8)
8.Values: 0-Hides the entire header(not recommended)
1-Title & menu bar with Exit , help ( buttons )
2-Displaying the title line
4-Displaying the button exit
8-To display active buttons on the screen ex: Back & Exit
16-Displaying the system menu
32-Displaying the application buttons
64-Displaying main menu button (new)
128-Deactivating the status bar
256-Deactivate the status bar
Regards
Veera