There's a scenario where default Crowd group memberships will not sync over to Confluence during initial login. If Confluence has synced with Crowd prior to the user logging in to Confluence, the user will be placed into the correct groups in Crowd but not in Confluence.
- User is added to default groups in Crowd

- User is NOT added to any groups in Confluence

This is alleviated during the next FULL sync from Confluence, whether automatic or triggered manually.
Crowd version: 2.7.2