For this model SBG7600AC2 when you login for the first time you will be using default login credentials which is username: admin and Password: password and then it will take you to customize the login credentials. please do check on the below article to access modem GUI

http://arris.force.com/consumers/articles/General_FAQs/SBG7600AC2-Web-Manager-Access

For modem user manual you can check on surfboard.com

To reset the modem to default login credentials you need to perform hard reset on the modem which will remove any customized settings made on the modem GUI.

http://arris.force.com/consumers/articles/General_FAQs/SBG7600AC2-Factory-Reset

Thank you SURFboard Moderator VIP for the reply. Unfortunately, this reply does not answer any of the questions. The walkthrough given is a very good tutorial for first time users. But this is not what was asked. Does anyone have information on the purpose, or function, as well as login credential info for the mentioned “Operation” tab?

I advise factory resetting the modem and attempting to log in to the GUI web portal using the default credentials. The default username is admin, and the password is password.

The credentials details are listed in the Quick Start Guide.

The GUI online portal will redirect you to update the login password when you enter the default credentials.

Could you share the screenshot regarding the operation tab on the GUI web portal?

As stated earlier, factory reset was already done. But there was no change in the credentials from the secret extra log in screen depicted at the top. Please find attached below the image depicting instructions on how to get from normative log in screen to the undisclosed page above.

In yellow is the “Operation” tab boxed-off, and which was referred to above. The Login credentials on each page are not the same!

Could you send us the screenshot after selecting the “operation link” on the GUI web portal?

Also, please share the firmware version for the modem.