No work change background-color

[johnsoul777]

.chat-window {
position: absolute;
top: 0.5%;
left: 33.3333%;
width: 33.3333%;
text-shadow: 2px 1px 2px #000000;
height: 22%;
max-width: 640px;
background-color: rgba(0, 0, 0, 0.250); <-------- This not work 👎
-webkit-animation-duration: 2s;
}