Contrary to many tutorials on the web, adding custom code to the theme’s functions.php file is not a good solution because if you change themes or the theme has an update, the custom code is lost. Which is why I always recommend the Code Snippets plugin.
I installed the Code Snippets plugin and added the code there. I had to use a different shortcode and function name. After I did that, the link showed up like it should.
So, that said, for some reason it is not working from the theme’s function.php file. I looked at the code and it seems right. I’ll leave it to your to delete the code from the functions.php file. I didn’t want to remove it without permission.
As a suggestion, I would move the link to the account page, since it is only a link.
Hope that helps!