upsell products not showing

Question

<?php if($this->getItemCount()): ?>
<div class="crosssell">
    <h2><?php echo $this->__('Based on your selection, you may be interested in the following items:') ?></h2>
    <ul id="crosssell-products-list">
    <?php foreach ($this->getItems() as $_item): ?>
        <li class="item">
            <a class="product-image" href="<?php echo $_item->getProductUrl() ?>" title="<?php echo $this->escapeHtml($_item->getName()) ?>"><img src="<?php echo $this->helper('catalog/image')->init($_item, 'thumbnail')->resize(75); ?>" width="75" height="75" alt="<?php echo $this->escapeHtml($_item->getName()) ?>" /></a>
            <div class="product-details">
                <h3 class="product-name"><a href="<?php echo $_item->getProductUrl() ?>"><?php echo $this->escapeHtml($_item->getName()) ?></a></h3>
                <?php echo $this->getPriceHtml($_item, true) ?>
                <button type="button" title="<?php echo $this->__('Add to Cart') ?>" class="button btn-cart" onclick="setLocation('<?php echo $this->getAddToCartUrl($_item) ?>')"><span><span><?php echo $this->__('Add to Cart') ?></span></span></button>
                <ul class="add-to-links">
                    <?php if ($this->helper('wishlist')->isAllow()) : ?>
                        <li><a href="<?php echo $this->getAddToWishlistUrl($_item) ?>" class="link-wishlist"><?php echo $this->__('Add to Wishlist') ?></a></li>
                    <?php endif; ?>
                    <?php if($_compareUrl=$this->getAddToCompareUrl($_item)): ?>
                        <li><span class="separator">|</span> <a href="<?php echo $_compareUrl ?>" class="link-compare"><?php echo $this->__('Add to Compare') ?></a></li>
                    <?php endif; ?>
                </ul>
            </div>
        </li>
    <?php endforeach; ?>
    </ul>
    <script type="text/javascript">decorateList('crosssell-products-list', 'none-recursive')</script>
</div>
<?php endif; ?>

my checkout.xml at /app/design/frontend/default/{myThemeName}/layout/checkout.xml

<checkout_cart_index translate="label">
        <label>Shopping Cart</label>
        <remove name="right"/>
        <remove name="left"/>
        <!-- Mage_Checkout -->
        <reference name="root">
            <action method="setTemplate"><template>page/1column.phtml</template></action>
        </reference>
        <reference name="content">
            <block type="checkout/cart" name="checkout.cart">
                <action method="setCartTemplate"><value>checkout/cart.phtml</value></action>
                <action method="setEmptyTemplate"><value>checkout/cart/noItems.phtml</value></action>
                <action method="chooseTemplate"/>
                <action method="addItemRender"><type>simple</type><block>checkout/cart_item_renderer</block><template>checkout/cart/item/default.phtml</template></action>
                <action method="addItemRender"><type>grouped</type><block>checkout/cart_item_renderer_grouped</block><template>checkout/cart/item/default.phtml</template></action>
                <action method="addItemRender"><type>configurable</type><block>checkout/cart_item_renderer_configurable</block><template>checkout/cart/item/default.phtml</template></action>

                <block type="core/text_list" name="checkout.cart.empty.widget" as="checkout_cart_empty_widget" translate="label">
                    <label>Empty Shopping Cart Content Before</label>
                </block>

                <block type="core/text_list" name="checkout.cart.top_methods" as="top_methods" translate="label">
                    <label>Payment Methods Before Checkout Button</label>
                    <block type="checkout/onepage_link" name="checkout.cart.methods.onepage.top" template="checkout/onepage/link.phtml" after="-" />
                </block>

                <block type="page/html_wrapper" name="checkout.cart.form.before" as="form_before" translate="label">
                    <label>Shopping Cart Items Before</label>
                </block>

                <block type="core/text_list" name="checkout.cart.methods" as="methods" translate="label">
                    <label>Payment Methods After Checkout Button</label>
                    <block type="checkout/onepage_link" name="checkout.cart.methods.onepage.bottom" template="checkout/onepage/link.phtml"/>
                    <block type="checkout/multishipping_link" name="checkout.cart.methods.multishipping" template="checkout/multishipping/link.phtml"/>
                </block>

                <block type="checkout/cart_coupon" name="checkout.cart.coupon" as="coupon" template="checkout/cart/coupon.phtml"/>
                <block type="core/text_list" name="checkout.cart.extra" translate="label">
                    <label>Checkout Forms Extra</label>
                </block>
                <block type="checkout/cart_shipping" name="checkout.cart.shipping" as="shipping" template="checkout/cart/shipping.phtml"/>
                <block type="core/text_list" name="checkout.cart.widget" as="checkout_cart_widget" translate="label">
                    <label>Shopping Cart Items After</label>
                </block>
                <block type="checkout/cart_crosssell" name="checkout.cart.crosssell" as="crosssell" template="checkout/cart/crosssell.phtml"/>

                <block type="checkout/cart_totals" name="checkout.cart.totals" as="totals" template="checkout/cart/totals.phtml"/>
            </block>
        </reference>
        <block type="core/text_list" name="additional.product.info" translate="label">
            <label>Additional Product Info</label>
        </block>
    </checkout_cart_index>

Answer 1

It's important to know that the cross-sells are displayed in the shopping cart page.

1) Check if you have set the config in the product in question : admin->catalog->manage products->select the product->cross sells in the right side bar

2) Check if you have well : <?php echo $this->getChildHtml('crosssell') ?> in app/design/frontend/{package}/{theme}/template/checkout/cart.phtml

3) Check if you have well the crosssell block name="checkout.cart.crosssell" in the checkout.xml else you can add it app/design/frontend/{package}/{theme}/layout/local.xml then add this:

<checkout_cart_index>
    <block type="checkout/cart_crosssell" name="checkout.cart.crosssell" as="crosssell" template="checkout/cart/crosssell.phtml"/>
</checkout_cart_index>

4) Reindex all

5) Clear your Magento and browser cache.