PPPoE not connected with 7 parameter setup on Huawei SW

hi everybody,
to day i have a problem with PPPoE client , when i connect RB750 with SW access of Huawei, with 4 parameter mode, RB750 dial up normal, so when i change to 7 parameter mode ( include : F/S/P:VL:VPC:VCI:) so RB750 can not dial, i don’t know why? who is help me Pls,

pls help me asap…

thanks all

sorry my Bad English.