I’ve given this a test-run and it appears the ‘private’ topics don’t show up in the invite topic search whether you have the group set or not. It’s a little similar to this topic Category (Search Priority Ignore) globally affect searches, though in this case the category hasn’t been marked as ‘ignore’. However, the workaround is similar:
The repro:
- Create Private group
- Create Private Category, with permissions for See|Reply|Create set for Private group only
- Create Private topic in Private category
- Create admin invite:
- Paste Private Topic link into ‘Arrive at topic’
- Select ‘Private’ group for ‘Add to groups’
- Save invite
- Use invite with existing test user - user follows link and is added to the Private group, and lands on the correct topic