Changing Blog Image Won't Work?

the website is http://sso.rocketpoweredhosting.com and the CSS code I am using is below. It is code that was given to me earlier this week and worked on another site, but not on this one for some reason?

.slide-entry-wrap .image-overlay-inside {
background-image: url(http://sso.rocketpoweredhosting.com/wp-content/uploads/2019/08/first-aid-kit.jpg);
background-repeat: no-repeat;
background-position: center;
}
.container_wrap { border-top: none; }