Taxonomy Sidebar view with Nodes
The Representative node relationship will show you a single representative node for your term, so that's not what you need in this case. Instead, try this:

Relationship: Taxonomy term: Content with term

Your results will now look like this:

Term A

Node 1

Term A

Node 2

Term B

Node 3 etc

Assuming this is not what you want, you can next add some grouping like this:

Under Format: settings set Grouping field Nr. 1 to Taxonomy term: Name.
Finally, in Fields, set the Taxonomy term: Name field to Exclude from display. Now you should have a list of node titles grouped by taxonomy term.