1. The LNS configuration is incorrect.
2. The configuration on the PC is improper.In this case, the problem is caused by an authentication failure due to inconsistency between the tunnel name sent by the PC to the LNS and the one configured on the LNS.
1. Generally, when a PC serves as the LAC, it sends its host name as the tunnel name. In this case, ensure that the tunnel name configured by running the allow l2tp virtual-template 1 remote command on the LNS is the same as the PC host name, or do not configure the tunnel name on the LNS.
2. You are not advised to configure the LAC name of group 1 of l2tp-group so that the LNS allows all LAC access.