Hi,
There are simply a few possibilities.
1. If a certain IP address is used, it is possible that the IP address prevents AA data from being sent to the Adobe server (3rd party restrictions).
2. Could you kindly confirm that all of the context data has been set up and correctly retrieved?
3. In his preferences, the customer can disable the JavaScript accepts.
4. If a user registers using another device or browser at some point
5. The customer may not be a fully engaged user.