I can't see "Visual" and "Text" icons on Edit Post box.

Hi, I'm Full F. Pro user. All of sudden, when I opened "Edit Post" and I can't see "Visual" and Text." Only I see is "Add Media" and "Add Form" icons. When I typed, they turned out "Text" style, not like Microsoft word style. All letters are "TEXT" "Visual" icon was disappeared. I can't write now and I need help. I don't know what to do. Please, please help me. Thank you so much.