Links in footer behave differently

In the footer of my new website I want to include a few links to other websites. However I have encountered a strange behavior. In one position the links work, in the other not. The code I use is as follows:

<div class="footer-widgets-wrap">
                  
                   	<div class="col-md-4"></div> 
                    <div class="col-md-4">
                    <!-- first time -->
                      <p><strong>Our partner vacation rentals in the Oltrepò Pavese:</strong>
</p>
                        <a href="http://vacation-rental-italy.eu/" target="_blank">Vacation rental Italy</a>

                       	<a href="https://www.amazon.com/dp/B01N7OY6DM" target="_blank">Living in Italy</a>
                     </div>
                    <div class="col-md-4" style="width:100%"><?php require_once('CodeSnippets/AddThis-code.html'); ?></div>
                    
                    <div style="width:100%; height:20px"></div>
                    
                    <div class="col-md-4">
                      <!-- Second time -->
                     <p><strong>Our partner vacation rentals in the Oltrepò Pavese:</strong>
</p>
                        <a href="http://vacation-rental-italy.eu/" target="_blank">Vacation rental Italy</a>

                       	<a href="https://www.amazon.com/dp/B01N7OY6DM" target="_blank">Living in Italy</a>   
                        
                      
                    </div>
                    <div class="col-md-4"></div>
                    <div class="col-md-4"></div>
                   
                                       
                </div>

As you can see I have used exactly the same external links. However the first time they work, the second time not. Can you explain me why they behave differently?