Possible reasons why you may not see Similar Topics after installation:
1) Did you enable Similar Topics?
When you first install Similar Topics, it starts off disabled so you can adjust the settings before it goes live. You’ll need to turn it on in the Admin Control Panel (ACP) to start seeing results.
2) Have you checked your permissions?
Similar Topics is set up with permissions that should allow Registered Users, as well as those with “Full” or “Standard” User Roles, to see it. However, it’s a good idea to review your Groups Permissions to make sure all the necessary groups have access. Note: Guests are not allowed to view Similar Topics by default, so you’ll need to allow them too if you want them to have access.
3) Have you purged your cache?
Sometimes, a quick forum cache purge is all it takes to get things working after installation.
4) Are you using a non-default board style?
If you’re using a custom style, there might be a compatibility issue. If that’s the case, please let us and the style author know so we can help resolve it.
5) Is your forum running on a MySQL database server?
Similar Topics currently supports phpBB forums using MySQL v4.0.1 or later with MyISAM and InnoDB table types. If your forum uses a different database, Similar Topics will only function on MySQL servers.
6) Is your forum new?
Similar Topics is designed to work best on forums with a lot of content. If your forum is new and has only a few topics, Similar Topics may not show results yet. This is because the extension ignores words that appear in more than 50% of your topic titles. As your forum grows, Similar Topics will become more effective.