CSS files may have not loaded properly

General
1

Hi everyone!
I’m a new member.
I meet a problem: I create a vaadin7 project. when I run in local host my UI (like template in vaadin project (have a button)) normal but when I deploy to appenginee, My UI don’t have button (just have text and text)
Please help me! thank you so much.
I see error : “CSS files may have not loaded properly”
18783.png

2

Please help me! thank you so much.