Checkbox doesn't want to check

My codes are the following. The checkbox doesn't want to be checked with the style I gave it.

 <div class="form-group">
    <div class="col-md-6 col-md-offset-4">
       <div class="checkbox">
          <input name="remember" type="checkbox" ><label>Wachtwoord onthouden</label>
       </div>
    </div>
 </div>'

And css:

col-md-4.control-label, #email, #password{
    margin: 20px auto;
    width: 300px;
    resize: none;
    font-family: 'Exo 2', sans-serif;
    font-size: 1em;
    outline: none;

}

.btn.btn-link, .checkbox{
            display: block;
            margin-top:20px;
            margin-bottom:20px;
            color: $white;
        }

[type="checkbox"]:not(:checked),
[type="checkbox"]:checked {
  position: absolute;
  left: -9999px;
}
[type="checkbox"]:not(:checked) + label,
[type="checkbox"]:checked + label {
  position: relative;
  padding-left: 25px;
  cursor: pointer;
}

/* checkbox aspect */
[type="checkbox"]:not(:checked) + label:before,
[type="checkbox"]:checked + label:before {
  content: '';
  position: absolute;
  left:0; top: 2px;
  width: 17px; height: 17px;
  border: 1px solid #aaa;
  background: #f8f8f8;
  border-radius: 3px;
  box-shadow: inset 0 1px 3px rgba(0,0,0,.3)
}
/* checked mark aspect */
[type="checkbox"]:not(:checked) + label:after,
[type="checkbox"]:checked + label:after {
  content: '✔';
  position: absolute;
  top: 3px; left: 4px;
  font-size: 18px;
  line-height: 0.8;
  color: $background_color_green;
  transition: all .2s;
}
/* checked mark aspect changes */
[type="checkbox"]:not(:checked) + label:after {
  opacity: 0;
  transform: scale(0);
}
[type="checkbox"]:checked + label:after {
  opacity: 1;
  transform: scale(1);
}

It's pretty weird since I use the exact same style for some other part on the website, but it does work on there. It should work on both this part as that part, right?