1. Check do you have editor.js in /public_html/styles/Supernova/template/editor.js

2. Go to the "Permissions" tab in your ACP.
Click on "Groups forum permissions"
Select "Registered users", then click on "Submit"
Tick the "All forums" box, then click on "Submit"

Set Permissions to "Standard access + polls". BBCodes will be working on those forums.