AUI tabs are alive and well
Are you adding your UI to your own page, or to an existing one? It’s possible that you are missing a web-resource
<dependency> on the tabs code.
atlassian-plugin.xml file, check if your feature code looks something like this:
<resource type="download" location="my/feature.js" />
<!-- ...your other resources etc. -->
If that’s not the problem, can you give us a little more detail on what you’re building, what you expected to happen, and what’s not working? Screenshots and copies of logs would be helpful in establishing more context.
Hope that helps!