Sidebar on single product page

Hey Sophieja23!

Please change the code you have posted from documentation to following one

#
# wrap single product image in an extra div
#
add_action( 'woocommerce_before_single_product_summary', 'avia_add_image_div', 2);
add_action( 'woocommerce_before_single_product_summary',  'avia_close_image_div', 20);
function avia_add_image_div()
{
	echo "<div class='four units single-product-main-image alpha'>";
}
 
function avia_close_image_div()
{
	global $avia_config;
	$avia_config['currently_viewing'] = "shop_single";
 
	echo "</div>";
}
 
 
#
# wrap single product summary in an extra div
#
add_action( 'woocommerce_before_single_product_summary', 'avia_add_summary_div', 25);
add_action( 'woocommerce_after_single_product_summary',  'avia_close_summary_div', 3);
function avia_add_summary_div()
{
	echo "<div class='four units single-product-summary'>";
}
 
 
 
function avia_close_summary_div()
{
	echo "</div>"; //close out the summary
	echo "<div class='four units single-product-sidebar'>";
	get_sidebar();
	echo "</div>";
}

Regards,
Yigit