When you run the pppd debug command, the output shows the following problems:
Peer is not authorized to use remote address address
Cause: You are using PAP authentication, and the IP address for the remote peer is not in the /etc/ppp/pap-secrets file.
Solution: Add an asterisk (*) after the entry for the peer in the /etc/ppp/pap-secrets file.
LCP starts but terminates shortly afterward
Cause: The password might be incorrect in the database for the particular security protocol.
Solution: Check the password for the peer in the /etc/ppp/pap-secrets or /etc/ppp/chap-secrets file.