Magento - Cancel Order not working

Question

Hello Magento Experts,

I have a strange issue in one of my Magento1.9.x site. In the admin panel, when I log in and then I click Sales -> Orders -> Edit any pending order, I click on cancel, it just refreshed the page and nothing happens.

To debug further, I created a clone of the site, and uploaded it on my server, in that I fixed the cancel order issue and I was able to successfully cancel my order.

So I went on the live site and uploaded the same code there, but on live site, I got an error on clicking cancel button: Invalid Form key, please refresh the page.

What I fixed is below :

In file: app/code/core/Mage/Adminhtml/Block/Sales/Order/View.php,

Before :

public function getCancelUrl()
{
return $this->getUrlSecure('*/*/cancel');
}

After :

public function getCancelUrl()
{
return return $this->getUrl('*/*/cancel');
}

Can someone please help me what can be the issue on live site?

Thank you.