Invalid Address in PPPoE server

I keep getting under addresses tab DI pppoe- and it will in red and user cannot connect internet, user is connected PPPoE server and assigned an IP, it is intermittent and random users, I brought one router back to workshop even changed its login details no different, tried another router with same login details and it happened on that.

I have search posts and noticed that a few people have come across this but I cannot find a resolution.

Any ideas.