Make mobile menu background an image not working

I'm trying to make the background of my mobile menu a photo. I've tried the code:

.Mobile-overlay-menu {
    background-image: url(https://static1.squarespace.com/static/6449809747dc621a3c0ac369/t/6478d3564221f7411e9cd6f0/1685640022458/pic.jpg);
}

and nothing is changing

I think your class name is incorrect. What is your site url? We can check it easier

blue-blue-6rrc.squarespace.com

It looks like you figured it out with this CSS code?

.header-menu .header-menu-bg {
    background-image: url(https://static1.squarespace.com/static/6449809747dc621a3c0ac369/t/6478d3564221f7411e9cd6f0/1685640022458/pic.jpg);
    background-size: cover
}