Suggested Topics not working for my community

Since I don’t know how long you’ve been set up, may I ask how many topics you have?
Can you set the suggested topics unread max days old to 60 and see if that makes any difference?

Also refresh your browser - especially if using Chrome. It has a habit of caching. Another tip is to open this in a new tab and close the old one. That often works when a simple page refresh doesn’t (in Chrome).