Hello,
The {confirm}{/confirm} code only inserts the link as a text. Most mail clients automatically detect the urls in the emails and convert them into links but not all mail clients do this.
You can write "{confirm}{/confirm}" in your email, select it then apply the link on it like this:
This would work with any link you want, but since this is a special code and not an url, you may need to make sure the link isn't modified by the editor. For this, select the zone containing your text then click the "Edit HTML" button:
Once opened, make sure there is nothing before the "{confirm}" code:
The screenshot is apparently too big, I wrote "Remove this automatically added path then save"