Hello!
Please also add "single-session" to
set service pppoe-server ppp-options
From accel-ppp docs:
single-session=replace|deny
Specifies whether to control sessions count.
If this option is absent session count control is turned off.
If this option is replace then accel-ppp will terminate first session when second is authorized.
If this option is deny then accel-ppp will deny second session authorization.