$row not properly echoing a row from mySql Database

I'm working on a website and would like to display user posts. I know how to create the row on the database and everything but from some reason, it's just not loading anything.

I have a mysqli connect code at the top.

Here's the PHP:

$sql = "SELECT MainPagePosts, PostUser FROM UserPosts";
$result = $mysqli->query($sql);


echo '<div class="UserPostsBox">';
if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
         echo '<p class="UserPost">'; $row["MainPagePosts"]; echo " | Posted By: "; $row["PostUser"]; echo"</p>";
     }
echo '</div>';
} else {
    echo "0 results";
}
$mysqli->close();

?>

Here's the CSS:

.UserPostsBox {
  position: absolute;
  z-index: 3;
  top: 450px;
  left: 480px;
  width: 350px;
  height: 550px;
  border: 3px solid;
  border-color: orange;
  overflow-y: auto;
}
.UserPost {
  color: #22262e;
  font-size: 30px;
  font-family: sans-serif;
  z-index: 3;
  width: auto;
  height: auto;
  position: relative;
  top: auto;
  bottom: auto;
  left: auto;
  overflow: auto;
  border: 3px solid;
  border-color: #22262e;
}

I've tried lots of things and don't know what to do.

Thank You

Also if you want to see the website click here https://johnpowers.000webhostapp.com/JohnSite/HomePageItems/JohnSite_HomePage.html