Why is My Image Not Showing Up in The Background?

I am currently working a website and ran into a issue with my code. I am trying to set an image as a background for my header. I have checked the path to my image, the spelling of everything, and have checked my syntax online. Everything seems to match, so I don't understand why my image is not poping up. Any help you guys can give would be amazing. Thank you. Below is my css code:

header{

text-align: center;                                                                                           
background-image: url("image/concert.jpg");
background-size: 700px;
height: 333px;
width: 500px;
}