I am having the same issue. It seems no /etc/pap-secrets or /etc/chap-secrets file are created, so pppd is unable to login.
Adding the following piece of code to Pre-Boot Script solves the problem (quick and dirty fix).
echo ""iames" * "PASSWORD"" > /etc/ppp/pap-secrets
echo ""iames" * "PASSWORD"" > /etc/ppp/chap-secrets
chmod 600 /etc/ppp/chap-secrets /etc/ppp/pap-secrets
*NOTE: replace PASSWORD with your corresponding password.