The CSS is not working on Tables in my HTML File

I’m trying to built a website for my project where the CSS seems to be working for every content of the html file except the table
The Html:

 <table class='table-full'>
            <tr>
                <th>S.N</th>
                <th>Full Name</th>
                <th>Username</th>
                <th>Action</th>
            </tr>
            <tr>
                <td>1</td>
                <td>ABC</td>
                <td>abc</td>
                <td>
                    Update admin
                    Delete admin
                </td>
            </tr>
        </table>

The CSS:

}
.table-full{
    width: 100%;
}