arris sbg7400ac2 Unable to login in with default admin username and password post factory reset. Keep getting Invalid user name or password, or your access has been locked due to multiple failed login attempts!

I tried resetting one more time and same results.  Able to get on the default wi-fi connection and browse but unable to access admin functions.

The SBG7400 shouldn’t have a default login. Password is created in the default state. If you’re running into the same login issue, try password as the default password. 

I tried no password and “password” same error.

The default username is admin and the password is either password or created by you when you first access the settings page.  
 

How did you get cusadmin username?

Did you try disconnecting the coax and factory resetting again? 

Then try setting it up (temporarily) without the coax connected? 

https://arris.secure.force.com/consumers/articles/General_FAQs/SBG7400AC2-Web-Manager-Access