The login-page background image disappear

Dear Sirs, My cPanel/Webmail login page should have a background image (login-whisp.png), but it disappear very suddenly early this week. I right click the browser to view the page source of the login-page and found that it not contain the below code which I search the code should be for display the background images : I had try the "Theme Manager" and duplicate/clone to created a new login-theme (not modify anything), changed using the new login-theme but still fail to get back the background image to display. Can someone please help to give a hint how to fix it ?! Thank you in advance. with best regards, Andy