Problem with CSS Styling menu


Hello there, It seems that the program that we write the codes has some problems. I don't know why but the codes are written correctly and you can't save and proceed with the code


share your code or problem, so that someone can help


Great because i'm a new user i can't upload pics. So i'm on 7/10 on CSS styling and my code for main.css is
.learn-more h3 {
the situation on index.html is

unfortunately before the h3 element the .learn-more element is not colored like its working but the program had let me submit the code.
Is the first part of CSS wrong or something somewhere because it doesn't let me submit the code



    <link href="main.css" rel="stylesheet">
    <link href="" rel="stylesheet">