G54 Surfoard Wi-Fi Model - Unable to Login to Web GUI

I’m sorry this will not be useful to your inquiry, but I am having the exact same issue. Newly installed G36 2 days ago. I was able to use the web GUI to set up, but now cannot get back into the GUI for additional setting changes. 

Should have prefaced my original post with my background: BS/MS in Computer Science and a Software Engineer for 33 years. 

Following is an update since original post:

1. Arris Surfboard Central app login (RESOLVED).
2. Arris WEB GUI login (via laptop and mobile phone). (RESOLVED).
3. NetGear Extender interface to Arris G54. (RESOLVED)
4. Arris G54 WPS button select to connect to NetGear Extender (ie. says new device added to network). (RESOLVED)
5. NetGear Extender connects to internet via Arris G54 router/modem. (UNRESOLVED)

Following are resolution comments for the above 1-4:

STEP 1:  Reset G54 Cable Model

1. Initially installed G54 Wi-Fi Cable Modem following instruction on the Quick Start Card and Surfboard Central app.  G54 installed ok and Username/Password defaulted to my email and a default factory password.
2. Detached coaxial cable to ISP and attached an ethernet cable from laptop to the G54.
3. Reset the G54 using the reset receptacle in the back and went to 192.168.0.1. Home Network Wizard is presented and prompts immediately for New Password. Default factory password changed where Username=admin (does not allow username to be changed).

STEP 2:  Login to Web GUI

1. Configured the Arris G54.
2. After configuration, returned to 192.168.0.1.and successfully logged in to the web GUI using Username/Password set in Step 1-3.

STEP 3:  G54/NetGear Extender Connect Using Arris GUI “WPS” Button

1. Attached coaxial cable to G54 and connected to ISP.  Once G54 is reset/configured/password changed, can login to online WEB GUI without issue.  No longer requires disconnect of coaxial cable and connect of ethernet cable. 
2. Added MAC address of NetGear extender to G54 router.
3. Attached an ethernet cable to NetGear extender and successfully connected to G54 router.
4. Selected WEB GUI → Connections → WPS → “Pair” software button.  Pushed the NetGear “WPS” physical button.  LEDs blink on NetGear device, WEB GUI informs device added but NetGear device does not connect to Internet.  In NetGear GUI, says “failed to connect to internet”.

General Comments:

1. Deleted the SURFboard Central app on my iPhone. It has DEFECTS and doesn’t seem to have options to actually ‘configure’ the G54 cable modem post install.  Also deleted the app because the required Username/Password to access WEB GUI doesn’t seem to be synchronized properly between Install database and runtime mobile app database. (Note:  Speculating about synchonized DBs from experience.) Also deleted the app because after downloading it again, the app prompts to install the G54 that is already installed and working?
2. The now replaced original Arris router/modem had a physical “WPS” button. There is no “WPS” button on the Arris G54.  It is now a Software Option in the WEB GUI where “WPS” first has to be ENABLED.
3. Contacting Arris Tech Support on Monday for assistance with getting the NetGear Extender to connect to Internet using the new “WPS” function in the WEB GUI.  NetGear device never shows up in the GUI like the other devices on the network after the successful pairing message.  Other devices on the network connect automatically once the router password is entered.  (Note:  No idea why Arris chose to make the “WPS” button a SW item vs a physical item on the router and why it’s now necessary for the end user to enable “WPS” and to also configure IP MAC addresses.  Extenders are common devices to add on the network, so not following the SW update logic that seems overly complex.)