the unit AF400 star only few sec and after disconnected from the network,.., and send this error form the CLI.
LOG_WARNING, pppoe: Too many PADI try
LOF_INFO: sent PADI
LOG_INFO, pppoe: timeout expired
LOF_INFO: sent PADI
LOG_INFO, pppoe: timeout expired
LOF_INFO: sent PADI
LOG_INFO, pppoe: timeout expired
LOF_INFO: sent PADI
this sounds like a PPPOE error. Maybe it could not log on to the DSL provider. Try disabling PPPOE and connected unit to a DSL modem that will do the login to the network or to a plain hub.