Deco M5 won't connect to fuzenet internet did at fist was like a dream then it just stopped and can't get it to reconnect no matter what I do

Hello, i got got a set of 3 Deco M5s today, but I cannot get them to connect to the internet I am on Plusnet in the U.K. and my old Archer AC750 connects fine using pppoe and I provide a username and