Why isn't my Knowledge Article Visible on my Community?
Knowledge on Communities is great, but is a complete PITA to set up. There are so many reasons why your articles may not be displaying.
Structural Setup
First, is the community set up right - go through Setting up Knowledge on Communities to make sure you have not missed one of the vital steps.
Is the Article Detail page visible to the Guest User
See Audience, Page Variations settings
Does the Guest User Profile have Read access on the Object for the Article Type
And the Custom Fields on the Article Type that displays the data that the Guest User needs to see.
Data Setup
Are the Data Categories visible to the Guest User Profile
Does the Guest User Profile have access to ALL the Data Categories that have been set on the Article.
See Salesforce Help https://help.salesforce.com/articleView?id=category_visibility_whatis.htm&type=0for a full explanation of who can see what.
Has the Article been assigned to a Topic
Testing
Can you navigate to the Article via the URL directly
Can you search on the Article
Does it appear in the Article Topic list.