When I open the Plugins area inside CC2018 - I notice that there are no Topazlabs Plugins in there, but! When I open Program Files\Common Files - there is a Topazlabs folder in there - and that is where my copy of Star Effects resides - and is working well in CC2018.
I am using Windows, so this is what my file path looks like...
C:\Program Files\Common Files\Topaz Labs
Hope this helps?