The bug occurs before the reference to cartRows. There is no .center-cart-items class in the snippet you gave, and if you delete the reference to it, your code works fine (see snippet).

Check your complete html source, the js reference to assign cartItemContainer is probably the problem.

function updateCartTotal() {
  //var cartItemContainer = document.getElementsByClassName('center-cart-items')[0]
  var cartRows          = document.getElementsByClassName('cart-row')
  for (var i = 0; i < cartRows.length; i++) {
    var cartRow         = cartRows[i]
    var priceElement    = cartRow.getElementsByClassName('cart-price')[0]
    var quantityElement = cartRow.getElementsByClassName('cart-quantity-input')[0]
    var price           = parseFloat(priceElement.innerText.replace('$', ''))
    var quantity        = quantityElement.value
    console.log(price * quantity)
  }
return (price * quantity);
}

console.log(updateCartTotal());

<div class="cart-row"> 
  <div class="cart-item cart-column"> 
    <img class="cart-item-image" src="#" width="100" height="100" /> 
    <span class="cart-item-title"> T-shirt</span> 
  </div> 
  <span class="cart-price cart-column"> $29.99</span> 
  <div class="cart-quantity cart-column"> 
    <input class="cart-quantity-input" type="number" value="2" /> 
    <button class="btn-remove" role="button">REMOVE</button>
  </div>   
</div>

I have recreated your code in codePen and it works fine:

https://codepen.io/SweetChillyPhilly/pen/xxpjyNQ

<div class="center-cart-items">
  <div class="cart-row"> 
    <div class="cart-item cart-column"> 
      <img class="cart-item-image" src="#" width="100" height="100" /> 
      <span class="cart-item-title"> T-shirt</span> 
    </div> 
    <span class="cart-price cart-column"> $29.99</span> 
    <div class="cart-quantity cart-column"> 
      <input class="cart-quantity-input" type="number" value="2" /> 
      <button class="btn-remove" role="button">REMOVE</button>
    </div>   
  </div>
  <div class="cart-row"> 
    <div class="cart-item cart-column"> 
      <img class="cart-item-image" src="#" width="100" height="100" /> 
      <span class="cart-item-title"> T-shirt</span> 
    </div> 
    <span class="cart-price cart-column"> $29.99</span> 
    <div class="cart-quantity cart-column"> 
      <input class="cart-quantity-input" type="number" value="2" /> 
      <button class="btn-remove" role="button">REMOVE</button>
    </div>   
  </div>
  <div class="cart-row"> 
    <div class="cart-item cart-column"> 
      <img class="cart-item-image" src="#" width="100" height="100" /> 
      <span class="cart-item-title"> T-shirt</span> 
    </div> 
    <span class="cart-price cart-column"> $29.99</span> 
    <div class="cart-quantity cart-column"> 
      <input class="cart-quantity-input" type="number" value="2" /> 
      <button class="btn-remove" role="button">REMOVE</button>
    </div>   
  </div>
</div>

JS:

function updateCartTotal() {
  var cartItemContainer = document.getElementsByClassName('center-cart-items')[0]
  var cartRows          = cartItemContainer.getElementsByClassName('cart-row')
  for (var i = 0; i < cartRows.length; i++) {
    var cartRow         = cartRows[i]
    var priceElement    = cartRow.getElementsByClassName('cart-price')[0]
    var quantityElement = cartRow.getElementsByClassName('cart-quantity-input')[0]
    var price           = parseFloat(priceElement.innerText.replace('$', ''))
    var quantity        = quantityElement.value
    console.log(price * quantity)
  }
}

updateCartTotal();

Your console log is working as expected.

So i suspect your issue lies outside of this code.