Hyperlink not working within CiviCRM emails
CiviMail is usually (and by default) configured to mangle the links in a civimail message in order to be able to track them. I suspect you've got a configuration issue which is preventing those mangled urls from working properly.
A mangled url typically looks something like this:
https://example.org/civicrm/mailing/url?u=21189&amp;qid=1478417
Solutions:

If you're in a hurry, you can just turn off the link tracking for your message.

CiviCRM has recently converted from a different url for such purpose (one with &quot;extern&quot; in the path) - if you've got an old link like that which is breaking, you probably want to update your civicrm version to fix the problem.


In any case, to help you further, it'd be useful to get details about the link that &quot;doesn't work&quot;, i.e. provide the url of an example and also what you're seeing on the screen when following that url.