C7000 Nighthawk ac1900 WiFi connection issue

I have  a  customer using Nighthawk combo modem WiFi  router  on Time Warner which  won't  make a WiFi   connection. I am not  in a tw service area  and  therefore trouble shooting  is a  problem.

Are  there any  known  common issues?  It is  a  business  class line from  tw and  it appears  to not  be getting  an  ip  address. There  are  other WiFi   devices  working  fine. The  product  has  connected  to  all  other WiFi  routers tested .

Is it  possible they limit  the  number  of  connections in  the  modem? I've  only  ever  seen  that set in the  router?

Thanks in  advance.