Hi @Patcha ,
Welcome to Trend Micro Online Community.
You can try this way:
1. Connect the doorbell camera to your home network.
2. Open the Home network security app > dashboard > timeline
3. Look for a notice where a device is trying to connect and grant them the permission.
if that didn't showed up, check if Device Approval Feature is turned on.
1. from the Home network security > Menu > settings
2. Under Network and Security > Access Control > New Device Approval and turn it on.
3. Wait for the app scan and detect new devices on your network > tap the notification to review and approve it
4. Follow the on-screen instructions to add it to your network.
Let me know if any of these works.
By the way, since you have that kind of set up. This might be useful to increase your security: How to protect security cameras with Home Network Security | Trend Micro Help Center