**Topic subscription emails not sent on reply**

I have set up topic subscriptions for a specific user group (board members) by inserting directly into the `wpforo_subscribes` table. When a new topic is created, subscribers correctly receive an email notification. However, when someone replies to the topic, no email is sent to the subscribers.

**Setup:**
- WordPress 6.x with wpForo (latest version)
- Fork FSE theme
- Email sending works correctly (tested with wp_mail())
- Subscriptions are inserted via PHP using `$wpdb->insert()` on the `wpforo_after_add_topic` hook
- Subscription records have `active = 1`, correct `userid`, `user_name`, `user_email`, `confirmkey`

**Database record example:**
```
itemid: 29 | type: topic | userid: 204 | active: 1 | user_name: [name] | user_email: [email]
```

**What works:**
- New topic notification is sent correctly to forum-level subscribers
- WordPress sends email correctly via wp_mail()
- In-forum notification bell works

**What does not work:**
- No email is sent to topic subscribers when a reply is posted

**Question:**
Is there a specific setting that needs to be enabled for reply notifications to topic subscribers? Or is there a requirement for how subscriptions must be created for the reply notification to trigger?