who will answer my question?   SUPPORT or a system user?

Could you help us with the model number?

Usually, to login to the GUI web portal, the username is admin. There is no option to change it. 

model G54     If the user name is to be “admin” which password should be used?

I tried the account password with out success.

If you are unable to login to the GUI web portal, I suggest resetting the modem.

http://arris.force.com/consumers/articles/General_FAQs/G54-Factory-Reset

After resetting the modem, please follow the steps to create a login password at the below given link:

http://arris.force.com/consumers/articles/General_FAQs/G54-Web-Manager-First-Time-Login

I just set mine up and it required my email address , then emailed me a password. 

I don’t see anyway to change the gui login or password (or enable access to someone else). I’m not doing a factory reset. 

Have you set up the surfboard central app on your phone?

If you set up the app on your phone, it will automatically create login credentials for the GUI web portal.

Open SBC app>Home>Access web interface>Email address and password to login in the GUI portal.

I did use the app but it made me use a password that it sent by email to me. Don’t see any way to change it now. 

I request to follow the steps on the below given link to find the password to login the GUI web portal.

http://arris.force.com/consumers/articles/General_FAQs/SURFboard-Central-Web-Manager-Access