This issue occurs because RADIUS Logical Line ID is not supported for Point-to-Point Protocol over Ethernet (PPPoE).
The feature is supported in PPPoEoA and PPPoEoVLAN confgiurations. This feature can be applied only toward PPPoE over ATM (PPPoEoATM) and PPP over Ethernet over VLAN (PPPoEoVLAN) (Dot1Q).
Note: This feature supports only RADIUS. TACACS+ is not supported.
For more information, refer to the Restrictions for RADIUS Logical Line ID section of RADIUS Logical Line ID.