Bootstrap can't select checkbox on iPhone

I can't select my checkboxes when I'm previewing on an iPhone. There's just one checkbox at the end of my document that DOES work, which is confusing me. The ones that don't work have this markup:

 <div id="advancedsearch-column" class="col-xs-12 col-sm-4">
     <div class="checkbox">
      <label>
        <input type="checkbox">
       Brand 1
      </label>
    </div>
 </div>

The one that does work has this markup:

<div class="form-inline">
 <div class="checkbox no_margin">
   <label>
   <input type="checkbox"> On special
   </label>
 </div>

There is a form tag surrounding everything. I tried adding a .form-inline class to the faulty checkboxes but it didn't seem to help. The checkboxes work fine on desktop.