This can have many different reasons, such as:
- Is a network connect (NC) role assigned to all users or do some only get some webbookmarks, SAM, etc.? If they doesnt have a sign-in policy configured that assigns them NC, they dont get a VPN IP.
- Did you configure that users can start NC manually instead of starting it automatically after login? Maybe they just didnt start NC, so they dont get a VPN IP.
- Is a client-side firewall preventing network connect from starting, do users get a message such as nc.23791?
- Maybe their session just expired, cause they are logged in for a while - then they are losing their NC connection.
Just check the user access log file and you will know why!