IIRC in Zerotier new clients are easily added, but traffic to and from them is blocked by default, until you approve them in the web interface.
New clients have to be approved before they can join. How would you not notice?
Where do you approve them?
The online control panel where you setup your private network in the first place. This is where you configure the IP range and other settings, and accept any devices that try to join.
It's too bad you mae these comments without actually having tried it.