If the link is working on the website, but when you click it in the Test email you see an error saying "This site can't be reached", it is very likely that there is a problem with CNAME records. This usually happens when you are testing the email at your office on your corporate network. A quick easy test for this is to click the link on your phone (assuming your phone is not on your corporate network). You can try something like geopeeker as well https://geopeeker.com/ to test the link.

The issue arises as your CNAME records are typically set on the public DNS server and not on your internal DNS server as well. If these CNAME records are not propagated to the internal DNS server, when you click a link at your office, the internal routing will not exist. The links will work for the general public, but not for anyone who is testing the email within the office network.

If your company has an internal DNS manager, to see the links working you will need to add the link and www2 CNAME records to it as well. Talk to your IT folks and ask them to set the link and www2 CNAME records on your internal infrastructure.

For more information about CNAME records setup, refer to this article: