So this is what my developer said.
thank you a lot for your message.
What he wrote is correct: when you create a user using our plugin, there is no one logged in in this instance of the WordPress call.
The user_register hook fires by default since we use the default WordPress functionality for that.
Why is there a logged in user required?
If so, you might need to create a custom message or ask the other developer for some support on how it is possible without being logged in.
Hope this helps!