you should attach the VPN pool to the role that will assigned to the VIA users after successfull authentication. For Windows and iOS clients the default VIA role is defined by the VIA authentication profile . For Mac clients this is represented by the default role in the default VPN profile. In the user role you have a L2TP pool parameter, add the VPN address pool that you want to use for the VIA clients here.
!
user-role "default-via-role"
pool l2tp "via-pool"
!
Regards,
Sathya